Spider Guardian Escape
It is possible to bomb jump out of the entrance to the spider guardian's room by means of glitchy spiderball tracks. This trick does not have any sequence breaking value as the game crashes once you shoot the entrance door again.
Once the fight starts, hold the control stick in a position somewhere between left and top-left (the exact position of the control stick seems to be a crucial factor, so experiment). Perform a double bomb jump. Once in a while, you will get stuck at the top of your jump on a glitchy section of track. Keep holding the control stick to maintain your position.
One of two cases will apply now:
i) you are close enough to the top that a single bomb jump will get you there. Just jump out, but it is worth laying some extra bombs as you reach the lip of the entrance tunnel just in case you don't quite have the height and find yourself scrabbling on the edge;
ii) you need more than a single bomb jump to get out. In this case, you will have to resort to the first two or three bombs of the TRHbj (it has to be a bomb jump that does not require you to land on the ground, as you will fall through the glitched section - the HBJ and its variants are the only jumps that work).
Similarly glitched bomb jumps can be performed up other tracks in this room. It is useless but possible to obtain the missile expansion during the spider guardian fight by draining half his energy, then using a 3BJ to the glitch and three or all four TRHbj bombs up to the top of the relevant spidertrack. You may then exit the spider guardian fight through the morph ball tunnel by the missile expansion if you wish, and leave the fight arena via the dark beam door without the game crashing. Coming back round and attempting to hit the blue entrance door again, though, will result in a crash.
It may be possible to return to the fight area via a TRHbj back into the morph ball tunnel, but this is definitely not easy.