To do the glitch:
1) Have two files, one with S+T all chaos emeralds present but inactive because of one super emerald.
2) Have second file with Knuckles, on the level you want to abuse.
3) Knuckles gets to a bonus ring, does check time reset (either by time over or just death, I can't remember) and soft resets the game.
4) On the first file, go to Hidden Palace.
5) Fly Sonic up and get the lightning shield.
6) Right before Knuckles, scroll the screen up, then fly Sonic there with Tails. To beat Knuckles without touching the ground or being super, jump when Tails is touching Knuckles's sprite. Do this 8 times. It's kinda difficult, but possible.
7) This breaks the Robotnik cutscene. Wait a little while, until Robotnik steals one of the super emeralds (yes)
8) Now hop on the super emerald.... and find yourself in the special stage.
9) Get the emerald or not, you will respawn at the bonus ring that Knuckles touched before soft resetting.
If you do it WITHOUT the "second file" trick it respawns you at an underwater, empty, glitched Angel Island, then when you fall and die it starts over from the intro cutscene.