Activate the following cheats by entering the corresponding codes in the Sound Test:

CHEAT FUNCTION - CHEAT CODE
"Batman" Sonic - PCM 04 DA 21
Cute Sonic - PCM 11 DA 09
Dj Mc Sonic - PCM 03 DA 01
Secret Special Stage - PCM 7 DA 7
Tails - See you Next Game - PCM 12 DA 11
That Freaky Sonic One - PCM 12 DA 25

Complete the game as Sonic to unlock Tails.

To see the best times of the game developers, press the following at the title screen: RIGHT(2), UP(2), DOWN, C.

At the title screen, press the following to unlock the option of selecting any stage: UP, DOWN(2), LEFT, RIGHT, B.

Unlock the following bonuses by performing the corresponding tasks in Time Trials:

BONUS - HOW TO UNLOCK
D.A. Garden - Have a total time less than 37'00 in Time Trials
Sound Test - Have a total time less than 4'00 in Special Stage Time Trials
Special Stage Time Trials - Have a total time less than 30'00 in Time Trials
Stage Select - Have a total time less than 5'00 in Special Stage Time Trials
Visual Mode - Have a total time less than 25'00 in Time Trials

ACHIEVEMENT - HOW TO UNLOCK
88 Miles per Hour (5 points) - Travel through time.
Just one hug is enough (5 points) - Get a hug from Amy.
Paradise Found (5 points) - Complete a zone in the Good Future.
Take the High Road (10 points) - Pass the upper Signpost in Collision Chaos Zone 2.
King of the Rings (10 points) - Collect 200 Rings.
Statue Saviour (10 points) - Find the angel statue in Wacky Workbench.
Heavy Metal (15 points) - Defeat Metal Sonic without getting hurt.
All Stages Clear! (15 points) - Finish the game.
Treasure Hunter (20 points) - Collect all the Time Stones.
Dr. Eggman Got Served (30 points) - Destroy Dr. Eggman's final machine.
Just in Time! (35 points) - Complete the Time Attack mode in under 25 minutes.
Saviour of the Planet (40 points) - Destroy all the robot teleporters and Metal Sonic holograms in the past.