Hi BBP, welcome back to the forums!
As far as I remember, at least one level required a patch to be solveable at all, and another one used the bomber-as-a-floater trick to survive a fall (making a lemming a bomber so that it oh-nos in the moment of hitting the ground, then assigning a builder to it to prevent it from actually exploding). I believe that was only possible in Lemmings Revolution.
I managed to beat all the levels without using any glitches ???.
A perfect example was "My Finest Moment". You can solve that level without the bomber-as-a-floater trick.
I'm sorry, did I say I was having fun replaying Lemmings? I've been stuck on King Of The Castle (Win95) for days!
Hope this helps:
Do you know about the "bridge wall" trick? If you make three lemmings facing the same direction builders one after the other they form a thick bridge that a lemming can't step over, hence why it's a "bridge wall". Use this trick to contain the lemmings after the lava pit in order to save some of your builders for climbing up the level.