Press Up, Down, Left, Right at the title screen. A number that corresponds to the starting level will appear on the top right corner to confirm correct code entry. Press Up or Down to select a level.
Approach a jump at 200 kph and press Down, Up at the top of the jump. The speed of your bike will remain at 200 kph. Then, press 1 while in the air, and press 2 just before your bike hits the ground. This will allow your bike to remain in the air for a longer amount of time.