Ruldra: Oh yes, Revolution is hard as nails. I mentioned getting bored of it last year but I played most levels as a teenager. Actually finished some levels in the last column, but never got close of beating them all.
IIRC one of the levels was unsolvable and required a patch to fix it. I don't recall the level name but lemmings fell down to their deaths right away. They were supposed to survive the initial drop but in the 1.00 version they didn't.
I did also beat a couple of the last ones but some others, waaay earlier, wouldn't budge. The difficulty really was all over the place.
And regarding bugged levels, there was one which also contained a borderline fall, the maximum height the lemmings could survive. The problem was that it was pretty much random. Sometimes they lived, sometimes they died. Changing the game speed/framerate affected the results. Was playing on Win XP, can't remember if I made it past. IIRC, it was a level where lemmings dropped from the box, walked for a second or two and then fell into an empy water tank. Some attempts, they went splat, some attempts, the landed without issues.