Dont think of this wrong... this is different than Sonic 3D Blast 5 (Unlicensed NES game).
Sonic the Hedgehog has a different level cycle than Sonic 1 (Mega Drive/Genisis).
Green Hill Zone
Scrap Brain Zone
Spring Yard Zone
Warp Scrap Zone
After Finishing the GameEdit
These are the extra levels avalible after you beat the game.
Floating Island Zone
Mirco Size Zone
Underwater Death Zone
There is a boss at every Act 3 of a level.
Mecha Sonic, Mecha Tails, Mecha Knuckles