Assassin's Creed Chronicles: India

(Difficulty, Missable dependent on version)

Depending on the version of the game that you're playing, this will either unlock naturally after your first playthrough of the game (standalone version), or you'll have to get the high score/fastest time in each stage (Trilogy Pack version). You DO NOT have to do this part on Plus Hard; it can be done on Normal/Plus mode.

If you are playing the Trilogy Pack version of the game, there are many high score video walkthroughs on YouTube that will help you out. I recommend THIS ONE by 360GameTV.