Unlocking Cheat mode
To use this cheat, you have to first unlock Debug mode by collecting 16 Silver or Gold medals from the Blue Sphere special stages (any 16 will do). Select Mania mode, highlight "No Save", choose the "Secrets" option, and enable Debug mode. Next, hold Square + X while "No Save" is highlighted in Mania mode to unlock the Level Select menu. This menu allows you to select any level, and fight the secret final Boss without getting all of the Chaos Emeralds. You can also play as Tails and Knuckles when you go up against the secret final Boss. To switch characters, press Square while "Sound Test" is highlighted. To add Tails to Sonic, press Triangle while Sonic is shown under "Sound Test".