Unlock all Levels + Soccer Game
Start your Dreamcast and choose ''New Game'' in the VM Menu. Enter the following letters: GYU. Do not choose ''END'' now, but type those letters (GYU) in again! After doing that, type three times any letters. Doesn't matter which ones they are. Now press the yellow ''X'' button. If you get back to the VM Menu by that the cheat has worked. If not, redo it! Now you can either create a new game on the normal way you are used to or choose one of the existing save games. The next save state you create or choose will have all levels unlocked and it will have the Soccer Game appear at the very bottom of the level list!
(for short: New Game -> type GYUGYUxxx (where x can be any letter) -> Press X button -> Create new game or choose an existing one for all levels unlocked)