Sonic Advance 2 Cheats (GameBoy Advance)

To get each of the new characters:

  To get Cream: Beat the Leaf Forest as Sonic. 
  To get Tails: Beat the Music Plant as Sonic. 
  To get Knuckles: Beat the Sky Canyon as Sonic. 
  To get Amy: Beat the game and get all seven Chaos Emeralds with Cream, Knuckles, Sonic,
and Tails.

If you beat the game and collect every Chaos Emerald with every single character, it will
unlock a new level for Sonic.

To unlock the Boss option (Time Attack Mode), beat the game and collect all Chaos Emeralds
with three characters.

To unlock the Tiny Chao Garden, beat the game and collect all Chaos Emeralds (any
character).