Sonic Rivals Cheats

In order to unlock certain skins you must complete story mode with certain characters.

To unlock Metal Sonic you must beat the game with Sonic, Knuckles, Silver, and Shadow. (In no particular order)

To unlock new cups (as well as obtain Chaos Emerald cards) for Cup Circuit mode, you have to complete Easy, Medium, and Hard challenges in specific zones in Challenge Mode as follows:

Hold down when the countdown starts, then when countdown gets to 1 press X and let go both down and X.