Play a full regular game. When you finish and return to the title screen, press C to enter the options screen and set the game to "Practice". Press B then C, then press START to exit the menu and start the game. The practice track will now have regular traffic on it.
At the title screen, hold (A+B+C) and press START.
Watch The Ending Cinema:
Set the rank to "ULTIMATE", stage to "2 RD 5 BOSS", music to "15", and sound to "25". Then hold (A+B+C) and press START.
Killing the guardian at the end of a level without losing any energy will give you a one-million point bonus.
At the options screen, select difficulty as "Hard", then go to the sound test and listen to any song for over a minute. The setting "Hard" will change to "Yea Right". Select this and start your game.
Sound Test/Difficulty Setting:
At the title screen, press R, L, D and U. While you're there, select songs 7, 4, 3, 7, 5, 8, and 1 in that order and you should now be able to set the games difficulty level.