Sonic Advance X is another unofficial Game Boy Advance title. It is very likely a fan-made game or ROM hack, not an officially released product from Sega or Sonic Team.  The specific details of the gameplay, plot, and developers would be known only within the community of those who created and played it. Further information would need to be sought out from relevant fan communities or ROM-sharing sites specializing in GBA homebrew and modified games.

Sonic Advance X

Sonic Advance 3 (J)(Cezar)