Im not sure how SNES version will register releaserates when im unpaused.
I believe release rate changes work the same way on SNES as in DOS (other than not possible to do while paused), and therefore should not be timing sensitive. In DOS, it's like this:
1) A new lemming comes out, say it's the Nth lemming.
2) At the same time N is out, the game takes note of the current value of the release rate, call it R.
3) It saves a copy of the value R, and use that copy to track how long to wait before the next lemming (N+1) comes out.
4) If you now make changes to the release rate, say from R to S, it doesn't affect N+1 at all, because the game is using a copy of value R to track when to make N+1 come out, it doesn't look at new values of release rate (ie. S). Instead S will affect N+2, because when N+1 does finally come out, we'll be at steps 2 and 3 again, and the game will then save a copy of the value S to track when N+2 comes out.
This is why I describe all the release rate changes as "change to value X after Yth lemming has come out". The exact speed/timing of changing the release rate to X doesn't matter, as long as the target release rate value X is reached sometime after Y lemming and before Y+1 lemming. The main problem is only that because SNES doesn't let you change release rate while paused, for very large changes, there may simply not be enough time between Y and Y+1 to finish making the change, making it impossible to do on SNES.
It's easy enough to test this on SNES emulator. On a level that allows for a low release rate value (so you are given some decent amount of time to make release rate changes), once after you see a new lemming come out (N), try cranking up the release rate a bit. You should find that the next lemming to come out (N+1) doesn't actually come out any faster compared to not having changed the release rate, only N+2 onwards are affected. If you want to make N+1 come out sooner, you actually needed to change the release rate before N comes out, not after.
But you can only cancel miner using digger or builder on SNES version.
Yeah, I already tested this on SNES a while back when we were still on Fun. I think it doesn't work because on SNES, the miner starts off not mining as deep as on DOS--on DOS the first stroke goes 2 pixels below ground level, but on SNES I think it only goes 1 pixel below. So given the same number of completed mining strokes, SNES will always be one pixel less deep compared to DOS, and I think that's enough to prevent on SNES the miner canceling miner move used in the DOS solution.
Good job on finding the alternate placement of the basher for the staircase trick.
Testing shows it actually also works on DOS version doing it that way; I should've tested more thoroughly a while ago when we were looking at Fun 29/Mayhem 9, I was too focused at that time on the exact way it was done and working in the DOS solution.