I couldn't figure these out quickly, that's for sure. I believe Kaywhyn has beaten all of these levels somewhat recently. I can't remember if he played this on superlemmini or Neolemmix though.
I played the pack on SuperLemmini a very long time ago. I unfortunately don't have any replays, but I know I have verified that they're all solvable except for "The Snow Palace" on that engine. If you go the natural way of building to get over the top near the exit, you run out of time before you even get up there. However, if an extra minute is added so that the time limit is 11 minutes, then it's solvable, though it really comes down to the wire on time. That appears to be the change you made for the NL version, as I think that was what I saw from a quick skim of the pack when I downloaded it for NL. I believe that was around the time I PMed you asking if the level is possible under the 10 minute timer from a few years back.
@messedupfaceI have not played the NL version of the pack yet, and I have plans to eventually do so, but I know that all levels are possible from the time I played the pack on SuperLemmini several years ago. I don't have any replays for the levels on that engine, but I can get a solving replay for the three levels that you weren't able to solve. From what I recall, these levels don't need any fancy tricks or anything (none of the pack does IIRC), especially given that this is a classic 8 skills only pack and that many of these levels are ones others have made and that Jeremy simply collected them and made any changes he thought necessary to make his own pack.