At the PRESS START screen press L + R, C-Left, C-Right, L + R. Now press START and hold Z and repeatedly press L at the mode select screen until "Cheat Mode" is displayed. You will now have access to various options.

Reset car

If your car crashes you don't want to go reverse then stop and then go again. to get out of your crash push left on the control stick and A+B+C-down+C-left to put your car back in the middle of the track.