All Stages Cleared! Achievement
All Stages Cleared!50
Clear Sonic Generations.
There are three levels to complete in the Genesis Era and there are Green Hill Zone, Chemical Plant Zone, and Sky Sanctuary. Once you complete all three Zone, the challenges acts will unlock. you need to beat one challenge from each stage in order to collect the boss key. You need to collect all three in order to face the Death Egg Robot. Once you collect all 3 keys, challenge Metal Sonic to a fight; beat him in order to get your first Chaos Emerald.
Once you beat the boss, you will unlock the Dreamcast Era Stages. Beat both Act 1 and 2, fight Shadow to claim his Chaos Emerald and beat at least three challenges. The Boss in the Dreamcast Era Stage is Perfect Chaos; Beat him to unlock the Modern Era Stages.
The fifth Chaos Emerald is just given to you; Same thing here, beat all the three levels to get a Chaos Emerald. Challenge Silver to fight to get his Chaos Emerald and then fight the Egg Dragoon to get seventh and Final Chaos Emerald.
In order to fight the Final Boss, you need to collect all seven Chaos Emeralds. One 1 is given to you, three are from Boss fights and the other three are from the Rival fights. The final boss is Time Eater, beat him to unlock Super Sonic skill set and to see the ending of Sonic Generations!