I think it's already known glitch, but here are some explaination. the last glitch mentioned is about getting to the phantom's castle earlier, apparently it's only for Game Gear:
Just to clarify, it's the Master System version where you can do the early Phantom Castle entrance. To quote from the video:
On the Master System version, if you do this, you'll get a game crash or if you do it one frame later you'll get into the Phantom's Castle early.
There's two, one-frame windows. The first frame causes you to load an invalid level which causes a red screen of death crash. The second frame enters the Phantom Castle early saving 1.6 - 1.7 seconds. All other frames have no effect.
It's risky, but if that 1.6 seconds is the difference between a dead run and a PB, you have to go for it. If I go for it, I mash after the Island cutscene and hope for the best.
