Q] Are there any cheats for this game?
A] There aren't, apart from this one little tip. Haggar starts with a larger life bar than Cody or Guy. If you want Guy or Cody to have the larger health bar at the start of the game, simply pick Haggar and then let yourself die until all your lives are lost. Continue the game when asked and then pick either Cody or Guy, and you'll notice that your health bar will be the size of Haggar's despite the fact that your not playing as him.
Q] Are there any differences between the original NES version and the GameBoy Advance version found on Capcom Classics Collection Mini Mix?
A] Not really. The GBA version adds a menu (activated by pressing the L and R buttons together) which lets you either continue the game, reset it, or go back to the main menu to choose one of the other games. The main difference with the two versions is in the price -the GameBoy Advance version sells for a fraction of the NES version on eBay.