Fewest different skills levels can be beaten with

[Proxima]

Frost is long overdue another look. I find the following improvements, all of which are hardly worth a replay:

Frost 7: bombers+builders, builders+bashers 100%, builders+miners 100%
Frost 15 improved to 2 types, builders+bashers 100%
Frost 16 climbers+floaters+builders 100%

[mobius]

Beginning with some not particularly interesting episodes from Lemmings Revolution;

5-4 Crowded House 100%
builders+bashers+diggers

[trap the lemming in the top with a digger/builder. Let worker work

5-5 One Way Ticket
bombers+builder+basher+miner+ digger.

Dig at beginning. Build up to the arrow wall like I did in other challenges, instead of climbing. I don't remember if you can afford to use any builders to stall lemmings but you may lose a few lemmings to the fall here. after flipping the switch on top, dig near the edge, you'll a couple more lemmings here to this fall. Once the digger is at a safe height blow him up to make a hole.
After the acid pit, mine, bash, use a bomber to go through the next thin platform. Build up to the left, you may lose a few lemmings again to the fall. Build up again, bash, build and use 1 final bomber to exit.
I save the minimum 40/50 with little room to spare though, it seems likely there's room for improvement.

6-1 Iron Curtain 100%
climber+basher+miner+digger

dig near the start so the water lemmings will make a drop to the water. Make a climber and use the right hand path, ignore the "iron curtain".

(first two skill level):
6-4 Escape to Victory
builders+miners

[theoretical 100%: using miner hole glitch, to trap weasels, then build him back to start area. I assume this is used in the max % thread]

[namida]

This Tricky 18 solution I used in the "What skills can't you live without" topic adds a different combination of 3 skills to the list; Floaters+Builders+Diggers. Attached it here as well. I updated the first post as well (only with this; I didn't update anything else).

[Proxima]

In doing the NeoLemmix equivalent of this challenge, I found a bombers + blockers + builders solution to Tricky 27, which I believe should work in DOS as well, but have not confirmed yet.

[Proxima]

Other matters arising from the NL equivalent of the challenge:

* Crazy 8 (KEEP ON TRUCKING) was solved with just builders+bashers in NL, but hasn't been confirmed in DOS yet.
* Taxing 2 (Watch out, there's traps about) has several more 2-type solutions in NL, in addition to the blockers+builders already noted. Bombers+builders won't work in DOS because timed bombers can't explode early enough, but the others should work.
* Mayhem 22 (A BeastII of a Level): namida found a bombers+builders solution in NL, not confirmed in DOS yet.
* Taxing 28 (POOR WEE CREATURES): I found a floaters+bombers+builders+bashers solution in addition to the already reported 4-type solution; it should work in DOS too. It's even possible the bomber might be dropped with some RR fiddling.

Also, Wild 15 was incorrectly filled in with Wicked 15's result, and this had apparently gone unnoticed for years and might have remained there for ever were it not for our NL investigations

[namida]

Taxing 28 improved to 3 types (Floaters + Builders + Bashers).

[LemSteven]

Other matters arising from the NL equivalent of the challenge:
* Crazy 8 (KEEP ON TRUCKING) was solved with just builders+bashers in NL, but hasn't been confirmed in DOS yet.
* Taxing 2 (Watch out, there's traps about) has several more 2-type solutions in NL, in addition to the blockers+builders already noted. Bombers+builders won't work in DOS because timed bombers can't explode early enough, but the others should work.

I'm not sure whether or not Crazy 8 builders+bashers will work in DOS.  The solution that namida found will not work in DOS due to time constraints (there are 80 lemmings in DOS).  Whether the same level of crowd control can be done with a faster release rate remains to be seen.

With that said, Bombers+Builders for Taxing 2 does work in DOS, and is now confirmed.  Spoilers below.

Taxing 2 Bombers+Builders

Start on the right side.  The first lemming builds to turn around and then builds at the water.  The second and third lemmings on this side bomb in the same spot to create a holding container for the crowd.

Meanwhile, the first lemming on the left side builds over the water, starting from the very edge.  One of the later lemmings builds to turn around, and then builds just before the drop on the left (ignore this far left lemming when he runs out of bricks).

Now focus on the two builders going over the water, one from each side.  Make each build again when he runs out of bricks, but make sure the left bridge is stretched as much as possible.  The right builder will hit the left bridge and turn around, while the left builder hits his head on a small vine and turns around.  When he gets to the bridge on the far left, make him build about halfway up; the goal here is to make a safe fall to the rock below.  Once he drops to the bottom of the level, just two more builders get him to the exit.

The only thing left is to release the crowd.  This is done with a single bomber, who explodes just to the left of the crowd's container.

[LemSteven]

* Mayhem 22 (A BeastII of a Level): namida found a bombers+builders solution in NL, not confirmed in DOS yet.

I can confirm this is possible in DOS, although technically I haven't fully executed it myself because I used blockers in lieu of timing my bombers.  The blockers are clearly not necessary if you get the bomber timings right, but I don't have the patience for that kind of thing right now.

Spoiler

3 bombers (one just before the foot of the cross, and two on the left side) restrain the crowd.  Meanwhile, a trailblazer does a bunch of building to circumvent the obstacles, going underneath the chandelier thingies and then over the hollow tree thingy, ultimately landing on the first of two statues.  The crowd is then released with a bomber, and the final statue and tree are handled with the remaining bombers.