I'm sorry dude, but S3K is not the hardest classic Sonic game. It is hilariously easy. Granted, none of the classic Sonic games are hard, Death Egg Robot in Sonic 2 aside, but still.
You want hard? Look into Sonic 2 on the Game Gear. You will lose all hair. (Or cheese it out and play the Master System version where you can actually see stuff, but still)