Okay Rick! You chose some pretty straight-forward ones (because SJ has already vidded these two strategies, but I think I can provide some tips).
Prison Island Normal Time:
Just do what SJ does in his video (provided that you've seen it). As for a simple tip just keep trying and trying until you have a time under 1:30. It's real easy once you get the hang of it and if you want a good score then just try to "Let the Speed Mend It" and collect lots of rings and the 1-Up to get a decent score along with your time.
EDIT #1: Oh' I also forgot. When you are at the end and you see those 3 rings in front of you light dash them so you can get a nice speed boost and head straight for the Goal Ring, but make sure you shot the one GUN mech out of your way. Hope this helps you Sub 1:30!!
Lava Shelter Hero Time:
Like SJ's video (provided you've seen this one too XD) charge a spin dash before you get on each rail. Now at the beginning there is a way to accelerate over the Egg Pawns but it all depends on when you press X (if you have the GameCube version it's X) if you time it corrcetly Shadow will accelerate right over the Egg Pawn on the right rail. Also, before you reach the 2nd defense system take the rail (instead of just going straight down). Also, before you reach the Goal ring just homing attack straight off the rail and position yourself so you'll just land on the Goal Ring like Apraxas does in his video (Yes, he made a video, but he only showed the ending of his run.)
Well, I hope these help. I can't be much help on these because I tried to stick to SJ's vids. Also, I have yet to do better on Lava Shelter - Hero but I prefer Dark mission anyway.