


Every stage has two sets of special key locations (note the plural), and the game chooses one randomly upon entering the stage. After you get your 10th chao, the special key is unlocked.

To unlock Knuckles, Amy, and Cream, you have to beat Act 3 of Sunset Hill, Toy Kingdom, and Cyber Track (respectively) with Sonic as the lead character. This guide has an in-depth guide for the current 100% route which includes a map of each area and hub, the general route to take, and the reasoning behind each route decision.
