In-game reset
Hold [Start] + [Select] + "A "+ [B] during game play.
Easy mode
Press [Select] at the main title screen for an easier game.
Run faster
Hold [B] during game play.
Retro stage
Clear all the five levels on Star Road by finding the hidden keys and locks in all of the levels. When you do this on the fifth level, a warp star should appear on the hill in the middle of the map. This will take you to the Special Zone, where you can play on 8 retro levels.
Avoid losing a life
Whenever you get to the two poles, press [Start], then go to save and continue. If you die later on, enable the "In-game reset" code. If done correctly, you should end up at the save point without losing a life.