Sonic Advance 2 Unlockables (GBA)

Sonic Advance 2 is a side-scrolling platform game in the Sonic the Hedgehog series, developed by Dimps and published by THQ for the Game Boy Advance. The game was released in Japan on December 19, 2002, in North America on March 10, 2003, in Europe on March 18, 2003. It is based on a modified version of Sonic Advance's game engine. Basic gameplay is an improvement on Sonic Advance, with much of the earlier features intact. Compared to its predecessor, Sonic Advance 2 contains more and larger levels, is more challenging, has an enhanced sound track, and offers better control over the playable characters.

There are seven zones, each containing two acts and a boss battle, and there is a final zone at the end of the game that consists purely of boss fights. Obtaining all of the Chaos Emeralds unlocks the Extra Zone. All characters can now perform various stunts when flying through the air and not curled in a ball (i.e. after being launched from a spring or similar). These are activated by holding a direction on the D-pad and pressing the R button. Some of these stunts can be used to destroy enemies. (Wikipedia)

Unlockables

Amy - Beat the game with Sonic, Cream, Tails, and Knuckles with all emeralds

Boss Option (Time Attack) - Beat the game with 3 characters, each having all 7 emeralds

Cream - Beat Leaf Forest with Sonic

Knuckles - Beat Sky Canyon with Sonic

Songs 58-63 on Sound Test - Beat Extra Zone as Sonic

Sound Test - Beat the game with 2 characters, each with all 7 emeralds

Tails - Beat Music Plant with Sonic

Tiny Chao Garden - Beat the game with 1 character, with all 7 emeralds

True Area 53 - Beat the game with Sonic, with all 7 emeralds. Then, beat the game with Cream, Tails, and Knuckles.

One of the best Sonic games ever: