Unlock all levels: After picking bike and rider go to the selection screen and press
Left, Up, Right, Down, Left, Down, Right, Up, Left and Modifier Airs Button

Unlock all bikes: At bike selection screen press
up, left, up, down, up, right, left, right and Modifier Airs Button

Unlovk all styles: At The style selection screen and press
left, up, right, down, left, down,
right, up, left and Modifier Airs Button