Level selct
While in the Sign-in Screen
Type Jeff as your name - access Advanced Levels
Type AaronFoo as your name - access Expert Levels
Type Megasaxon as your name - access all levels/AIs

Cheat mode:
Type in cheats while you are playing, and an icon will appear in the top right of the screen.

Code - result:

BLAST - Blasts all the AI cars away from you.
GLIDER - Drive of cliffs and fly like a glider.
SPIDER - Drive on almost any surface.
SLEEP - Makes AI cars drive like they are asleep.
TIMEWARP - Makes AI cars go slow mo.
LUNAR - Low Gravity.
HOVER - Makes car hover.
APOLLO - Hold ALT and car will take off like a rocket.
LIGHT - Gives Impression of driving at light speed.
SLIPPY - Makes AI cars slip out
BOMB - Press ALT to fire Mortar Bombs
JUMP - Press ALT to Jump
STICKY - Gives more traction
BURN - Press ALT to shoot Fire Balls.
ICBM - Car acts like a missile.
LAUNCH - Hit "a" to launch a car,
"z" to move in the direction you're facing.
SUCK - Cars gravitate towards each other.
TWISTER - AI cars get whipped around by an invisible tornado.
WARP - Other cars crawl over track.