The Japanese Sonic Team website had released some new information and images for Sonic Advance 2. (Note: I used a translator for some of this, so it may not be 100% accurate)
Firstly, the rather surprising return of Zero – it seems that he now resides in the bonus stages, now using an isometric runaround style similar to the Sonic CD bonus stages. It seems you have to defeat Zero to get a Chaos Emerald.
Also, some of Cream’s moves are described.
Chao Attack
Apparantly this move is similar to Sonic’s homing attack, probably meaning that there is a certain amount of automatic ‘lock-on’ to the enemy (be honest, you’ve been wanting to do this for a long time :b).
Fan Flight
This move looks somewhat similar to Tails’ propellor flight. It seems enemies are also damaged on your way back down.
Chao Rolling Attack
As far as I can tell, this move is simply a spin attack but with Cheese the Chao doing the same thing, therefore increasing the chance of hitting the enemy.
There also seem to be new moves for all the characters. The first seems to be a ‘boost’, which as far as I can tell is where your character speeds up greatly after an extended period of running. This may take up rings, and it is possible only Sonic can do this.
Other moves are ‘trick actions’, which seem to be a kind of vertically downwards attack, including Knuckles’ Drill Claw from SA2.
Also included on the new sub-site are some downloads including wallpapers and a movie. Check it out here. If you’re having trouble navigating, the first link on the nav bar is home, the second some info on Cream and Cheese, the third info on new character moves, the fourth special stage information, the fifth some as yet undisclosed ‘secrets’ (Hmm…) and lastly the downloads section.
Source: Sonic Team