Sonic The Hedgehog Advance Cheats (GameBoy Advance)

Highlight Sonic at the character selection screen. Next, highlight Tails and press Down.
Then, highlight Knuckles and press L. Finally, highlight Amy and press R. Highlight Sonic
and press A to select him. Tails will follow you during the game, but cannot be
controlled.

Collect all seven Chaos Emeralds for all characters. Successfully complete the game as
Sonic to unlock the Moon Zone.

Play the first level. Press Start + Select + A + B to reset the game. Go to the Chao
Garden and you will have the rings that were collected, but reset at the start of the
next act of the level.