At the sound test screen (must be unlocked):
Enter the following tracks: PCM 12 DA 11. After seeing a picture of Tails, start a new game, holding down A + Start.
It is okay to skip the intro. Just ensure you are holding down A + Start by the time the zone loads up. You will know if it worked if you see your X and Y coordinates ticking on the upper right hand of the screen.
B button: Debug mode.
A button: Cycles object (while in debug)
X button: Places object (while in debug)
Achievements will be disabled and Zone/Act times will not be recorded while Debug Mode is active.