To beat the 3rd boss quicker, get close to him and don't move. You can punch him when in the air.
Get two GBA's and a gba link cable then put Rayman 3 game and put it in one of them(leave the other one empty). then turn on the one with Rayman 3 in it and link the GBA's together. when on main screen of Rayman 3 select multiplayer then select single pak link and turn the other GBA on then tadaa your in a plane and your battling the other GBA!
After collecting 100 orbs, link your Gameboy Advance to Rayman: Hoodlum Havok on the Gamecube to unlock 10 new bonus levels.