CheatCodes.com has all the official Sonic Advance GBA cheats to unlock everything. If you know of any that we don't have, please let us know.
All published and official codes as of Wednesday May 22, 2013 for Sonic Advance are shown below.
In character select, highlight sonic and press up on the directional pad. Then go to Tails and press down. Then go to Knuckles and press the left trigger. Finally go to Amy ant press the right trigger. Enter on Sonic and you will here a chime. Enter a level and tails will follow you.
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