Metal Sonic:
Beat the game with Sonic, Knuckles, Silver, and Shadow to unlock Metal Sonic. Alternately, collect the “Metal Madness”, “Metal Overlord”, and “Neo Metal Sonic” cards.
Knuckles’ leather shoes:
To get Knuckles’ leather shoes, get the Buzzer 2002, Coconut 2002, and Turtloids 2002 cards.
Silver’s leather shoes:
To get Silver’s leather shoes, get the Chaos 2 (1998), Chaos 4 (1998), and Chaos 6 (1998) cards.
Sonic’s ice costume:
To get Sonic’s ice costume, get the Miles “Tails” Power 2002, 2004, and 2005 cards.
Sonic’s leather suit:
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.
Skins:
Unlock the following skins by performing the corrresponding tasks:
Knuckles – Beat Story mode with Knuckles.
Metal Sonic – Beat Story mode with Metal Sonic.
Shadow – Beat Story mode with Shadow.
Silver – Beat Story mode with Silver.
Sonic – Beat Story mode with Sonic.
Cup Circuit mode cups:
Unlock the following Cup Circuit mode cups by beating the easy, medium, and hard challenges in the corresponding zones in Challenge mode:
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