Story related, can't be missed.
The achievements for the difficulties may or may not stack. They are glitchy, but you can obtain them all in 1 full playthrough, plus completing the final mission 2 more times, by using the method outlined in step 1 of the roadmap above. This is the hardest difficulty mode and you will likely be restarting your missions frequently. Using a walkthrough will help out and should shorten your play time if you know what to do ahead of time.
Simply complete the game on professional difficulty, to unlock this achievement.