In order to reach 100% synchronization in Boston, you will have to complete 9 Sequences, 4 Side Missions, and recover 3 Lucid Memory Artifacts. Here's the breakdown of each requirement:
Sequence 1: Prison Break
Kill 3 guards undetected.
As soon as you open the door to the large warehouse area, head down the steps and follow the next set of stairs to the ground level. You will notice two guards on your right having a conversation, and one further behind them near a hay cart. Activate your Wolf Cloak using to sneak past the guards and hide in the hay cart. From here, kill the lone guard next to the hay cart. Next, use the to whistle in order to attract the next guard. Once he peers into the hay cart, kill him. Lastly, activate Wolf Cloak again, hop out of the your hiding spot, and sneak up behind the Heavy Guard. Tap to subdue him and the constraint is complete.
Sequence 2: Sky World Journey
Save all the eggs (3)
Once you climb to the top of the tree, you will have to save all three eggs in the Eagle's nest from a group of Bobcats. As they approach the nest, they will pounce at you so be ready to follow the on-screen buttons prompts in order to counter dodge them in time. In total, there will be about 5 to 6 Bobcats that you must kill before the constraint is complete.
Chain 3 Eagle Flights, twice.
This should come naturally by the end of the Sequence. As a note, make sure to be looking up and press before you land on a rock or tree, in order to fly to the next location before you actually land and exit Eagle Flight. If done correctly, the constraint will be complete by the time you land on the last of the three thin trees as the Spirit Eagle flies away.
Avoid all obstacles.
This constraint is self-explantory. After performing the Leap of Faith off the treetops, you will now enter a flight sequence where you must fly through a canyon. Simply avoid hitting any rocks or walls and you'll be in good shape. If you find yourself messing up during the tight corners or low swoops, you can always restart your last checkpoint to retry.
Sequence 3: Dive Bomb
Kill all guards while remaining undetected.
There are a total of 5 guards in the warehouse. If you mess up at any point during this, remember to restart your checkpoint. Hop in the hay cart in front of you right away! If you wait there long enough, one guard will eventually walk by. Whistle in order to have him approach, then take him out. If you wait a little longer, a Heavy Guard will come by too. Whistling does not work on him, but he will eventually stop right in front of the hay cart which will allow you to take him out. Now, we'll need to kill the last 3 guards with an Eagle Assassination while remaining undetected, so refer to the second constraint below.
Perform 3 Eagle Assassinations in the warehouse.
In order to perform an Eagle Assassination, you will need to use the in order to zoom in, and lock onto a target. Once you are locked on, hit the to enter Eagle Flight and Connor will swoop down and assassinate the target instantly. From the hay cart, use Eagle Flight to fly to the furthest barrel on your left. Quickly look down and lock onto the lone guard standing there. Tap again to perform an Eagle Assassination. Run back to the start of the warehouse and after some time, a guard will come inspect the area of the guard you just killed. Use the same method as before to kill him. For the last guard, fly to the top of the rafters and target him for the last Eagle Assassination.
Use Eagle Assassination to kill Franklin.
Once you regain control on Connor after a short cutscene, use Eagle Flight to get to to rooftops. From here, you must chase Franklin as he runs away. Once he crosses the streets via the cable wire that runs across the houses, target him and use an Eagle Assassination to finish him off.
Sequence 4: Consequences
No Constraints to complete.
Sequence 5: Return to Sender
Capture 2 of the opponent's pieces.
Good old checkers. You should know how to play, so just play against your opponent and he will move certain pieces into positions that leave him vulnerable to defeat. If you mess up, remember to restart the checkpoint. If you do not know how to play checkers at a base level, this may take several attempts. The AI difficulty seems to be set to Novice or Beginner, so he should be moving his pieces into positions where you will easily be able to "jump" them.
Kill both sentinels within the time limit.
The timer seems to appear once you kill the first sentinel. It is suggested to deal with the guard on the left first, who is inside the roofed boat structure. Use your Eagle Flight to reach him, then take him out quickly with any weapon you have available. Now quickly exit this structure and make a jump towards the second sentinel. While free falling, you will be able to use your Eagle flight on a nearby beam in order to reach the second sentinel on the raised platform. You should be able to finish him off before the timer runs out.
Sequence 6: Man of Mettle
Steal the horse undetected.
This can be a little tricky. While there are many, if not countless, ways to approach this Sequence's constraint, I found it easiest to approach the fort from the front gate. You will notice a guard and his attack dog stationed here. Round the fort's wall to the right and continue until you are running against the back wall. From here, use Eagle Flight to soar to the top of the wall. Now, use Eagle Vision to locate the horse and you will notice it is right ahead of you, down some steps. Use your Wolf Cloak ability to sneak past the guards stationed on the wall and head down the steps to mount the horse. The constraint is complete once the horse is mounted.
Sequence 7: Pieces in Motion
Use 3 contextual attacks during the bar fight.
This simply means using environmental attacks in the bar during the fight. You will notice certain parts of the bar are glowing, such as a chair. Lead your enemies towards these items and when you counter their attacks using , Conner will use the environment to his advantage. I suggest using the chair, the table, and the barrel right near the bar counter. There are 9 enemies that you have to fight during this section so do not worry if you eliminate the first three guards without using contextual attacks.
Remain undetected during the investigation.
Again, there are countless ways to approach this constraint. I found it easiest to hop in the bush to the right of the starting area and use bait to lure the guard dog away from the main entrance. Once he is distracted, use Wolf Cloak to approach the main gate and take cover in the bushes there. Once your Wolf Cloak recharges, active it and head through the main entrance. Follow the dirt path down the center of the fort and hop into the bushes to your right. Use some bait in order to distract a dog further ahead, and use this opportunity to investigate the clue in the middle of the road. After inspecting the clue, you should see a couple tents up towards your left with a bush nearby. Hide in that bush and allow your Wolf Cloak to recharge again. Use Eagle Vision to find the next clue, and distract the dog again before advancing towards the second clue. After viewing this clue, sit yourself in the bushes just beyond the hay cart right in front of you. When your Cloak is fully charged, drop some bait one last time to distract the last couple of dogs, and then use your Cloak to reach the witness.
Sequence 8: Aquila Unchained
Remain undetected while stealing the uniform.
This will be easier than expected. As soon as you regain control on Connor, use Eagle Flight quickly to catch up to the guard and subdue him. You will most likely attract a few guard in the area, so quickly switch to Wolf Cloak and sit tight while a few guards pour into the area. Use your Wolf Pack ability to kill some guards without much effort, and pick off any remaining guards while cloaked. Once the area is clear, pick up the guard you subdued, and carry him back to Franklin. If done correctly, it should be a short walk back, and you would only have had to kill about 3 to 4 other guards.
Use an Animal Power to kill a guard menacing Franklin.
Use Wolf Cloak and head north down the alley on your left. There will be two guards here. While Cloaked, make sure you have the Assassin's Blade equipped. Proceed to kill both guards and the constraint is complete.
Remain undetected while protecting Franklin.
From the alley you just killed both guards, take a left and head straight down the road. Use your Cloak and eliminate the Heavy Guard standing at the opened gate. Head through this gate and follow Franklin to the left. On the way, two guards approach Franklin from the left side of the streets. Use Cloak to eliminate them both. Quickly kill the one or two guards who are patrolling the right side of the streets and come running to aid their fallen comrades. Franklin will turn left down a wide street, and there will be two Heavies to the right. Take them out while cloaked and head through the alley they were guarding. At this point, you are now safe to proceed behind Franklin as he approaches Faulkner.
Sequence 9: Escape to New York
Save all the crew members.
Quickly eliminate the two Snipers at the edge of the dock. Now, turn around and begin fighting the horde of guards. Make use of your Wolf Pack in order to eliminate the enemies with ease. After clearing the first wave of enemies, the game will warn you to prepare for another wave. During the second and third waves, you'll need to rely more on luck than speed. Faulkner's men have reached the boat at this point and begin bombing the docks. There is a high likelihood that some of the crew members will be weakened and killed by these bombings so eliminate the enemies quickly and hopefully, none of your crew members die. Be sure to also make use of your Wolf Cloak to confuse the enemies and obtain double assassinations when they are in the midst of battle. If you mess up, you can always restart the checkpoint.
Kill Putnam while using an Animal Power.
As soon as you regain control of Conner, activate Wolf Cloak and rush towards Putnam. Tap to assassinate him and enjoy the cutscene!
For this Side Mission, you must attack a total of 4 conveys around the area of Boston and set their captives free. While roaming around Boston, you will get a notice on your screen that there is enemy convoy nearby. Open up your map, and set a waypoint towards it. You can work on this during or after the storyline. There seems to be a set location near the top of the district that you can keep revisiting to complete this Side Mission (see picture below).
Help the Hungry:
For this Side Mission, you must feed a total of 5 civilians around Boston. While roaming around Boston, you will get a notice on your screen that there is civilian nearby who needs your help. Open up your map, and set a waypoint towards them. You can work on this during or after the storyline. There seems to be a set location near the center the district that you can keep revisiting to complete this Side Mission (see picture below).
For this Side Mission, save a total of 4 civilians before they are executed by Bluecoat guards. While roaming around Boston, you will get a notice on your screen that there is civilian nearby who needs your help. Open up your map, and set a waypoint towards them. You can work on this during or after the storyline. There seems to be a set location near the left most part of the district that you can keep revisiting to complete this Side Mission (see picture below).
For this Side Mission, you must defend 2 civilians who are being attacked by wolves around Boston. While roaming around Boston, you will get a notice on your screen that there is civilian nearby who needs your help. Open up your map, and set a waypoint towards them. You can work on this during or after the storyline. There seems to be a set location near the top left of the district that you can keep revisiting to complete this Side Mission (see picture below).
Lucid Memory Artifacts:
After Sequence 3, Adams and Kanen'tó:kon advise Connor that they should meet up. This is when Boston becomes fully accessible. Before heading to Sequence 4, you'll notice an Artifact icon on your mini-map directly in front of you! Head to the rooftops to find the musket (pictured below, bottom-right of the map).
As you approach the bottom of the district (before the farm/rural area), the second Artifact will appear on your map. This Artifact is a small grey crate. It is surrounded by plenty of guards so prepare for a lengthly fight (pictured below - bottom-left on the map).
While exploring the northern part of the district, the third Artifact will eventually appear on your map. The hat is located on top on a wooden table, near a guard's post (pictured below, top of the map).
The main missions and their sync goals were excellent to decent, but wow were the side goals awful. I literally had to return to the same place 4 times to save the civilian from the redcoat and I'm pretty sure I stopped the same convoy three times judging by the surroundings. Raise your game Ubisoft.