Sonic CD Cheats - PC

Cheat Mode
Press [Down], [Down], [Down], [Left], [Right], [Space] at the title screen to enable the sound test screen and chat mode. Enter and play one of the corresponding sound combinations to activate the corresponding cheat function.

PCM12, DA11 - Debug mode
PCM07, DA07 - Bonus levels
PCM03, DA01 - Display artwork
PCM12, DA25 - Human-faced Sonic
PCM04, DA21 - Hercules Sonic
PCM11, DA09 - "Revenge of the Mutant Artwork"

Level Select
Press [Up], [Down], [Down], [Left], [Right], [Space] at the title screen. You can choose any past, present, or future level to play. However, when you warp or finish the level you will return to the title screen.

Development Team High Scores
Press [Right], [Right], [Up], [Up], [Down], [Space] at the title screen.

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