(updated, thanks for re-uploading my playthrough!)
This game just got in my mail today. The cartridge art says something like Sonic Fighter Sonic 3, but the Title Screen says Fighter Sonic. Also, that same music you've heard in that Rayman GBA pirate will loop over and over, getting on your nerves. Sonic attacks by throwing spin dashes at his enemies and jumping on top of them. The B-button jumps, while the A-button attacks. You can jump higher by holding up on the d-pad.