In order to unlock certain skins you must complete story mode with certain characters.
Silver Skin - Complete story mode with Silver.
Shadow Skin - Complete story mode with Shadow.
Knuckles Skin - Complete story mode with Knuckles.
Sonic Skin - Complete story mode with Sonic.
Metal Sonic Skin - Complete story mode with Metal Sonic.
To unlock Sonic's leather suit, get the Sonic The Hedgehog, Sonic The Hedgehog 2, and Sonic The Hedgehog 3 cards. To unlock the gloves, get the Cream The Rabbit, Cheese, and Cream and Cheese cards. To unlock the shoes, get the Sonic and Amy, Amy Rose 2004, and Amy Rose 2005 cards.
Successfully complete the easy, medium, and hard challenges in the indicated zone in Challenge mode to unlock the corresponding Cup Circuit mode cup:
Blue Chaos Cup: Death Yard Zone
Cyan Chaos Cup: Colosseum Highway Zone
Green Chaos Cup: Forest Falls Zone
Grey Chaos Cup: Complete every challenge in the game
Purple Chaos Cup: Meteor Base Zone
Red Chaos Cup: Sky Park Zone
Yellow Chaos Cup: Crystal Mountain Zone
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