OMFG 1 -
You want it, you got it! Nice 5-of-everything level to start off the rank! The skillset is somewhat restricted, especially considering the huge landscape, but there's still some leeway if you're efficient in your skill usage.
OMFG 2 -
Keep 'em busy Not difficult, just tricky. As the title suggests, the trick is to keep the others busy to give enough time for one lemming to bridge the gap to the exit. How achieve this is not easy. However, I was able to contain all but one of them in the starting area with builders and having one for the end.
OMFG 3 -
Fire in the hole Nice puzzle! Other than figuring out how to get through the bidirectional OWW (bash to the right in the upper half, bash to the left in the lower half), the only challenging thing is how to isolate a worker lemming. Getting a second is easy, since there's a climber for that. The timing to send the climber is not difficult so that it can use the stoner step to bash the OWW on top.
OMFG 4 -
Talent buried deep within Somewhat difficult due to the very restricted skillset. Working out how to free all the preplaced lemmings stuck inside the pillars is not easy at all. The most obvious is with a digger, but then there's also making sure they can still use the path forged to go to the right. I didn't have to use the disarmer to disarm the trap, so my solution might be a backroute? Also, I have several skills leftover, and my solution almost fails had the glider almost gotten past the exit at the end.
OMFG 5 -
Controlled overload More difficult repeat of ROFL 10 with the addition of slowfreeze AND radiation. Here, I avoided the slowfreeze completely and only used the radiation in my solution. I don't collect one of the blocker pick-ups either (decoy maybe?) and I have a climber leftover. Also, looks like this is the level that I encountered the solid ceiling in Pit Lems, and so this escaped me completely for OMFG 20. Then again, I think it was a very quick surprised reaction. So you see, I was aware of the solid ceiling, it just felt like an extremely fast passing remark since my attention was elsewhere, being on the timers on those that went through the radiation.
OMFG 6 -
Don't believe in prophecy Very nice and easy level using stoner steps to make one long continuous basher tunnel

OMFG 7 -
Lem in motion Another very nice, easy and short level!
OMFG 8 -
Walking in Lemphis The title is obviously a reference to Memphis. Nice looking level that's a bit of a tricky 2-of-everything level. Not too hard, though.
OMFG 9 -
Disintegrated Easy level, but that's probably because I backrouted the level. I have a builder leftover.
OMFG 10 -
Going down the hard way Ok, I consider this a very pointless repeat of WTF 9, since there's pretty much almost no difference between the solutions of the levels other than finding some way to get a lemming to turn around to bash since no there's no cloner this time. I probably could had gone 1 over the save requirement as well had the basher lemming been a bit higher, but to do probably requires tweaking the RR.
OMFG 11 -
You had it coming Really easy 10-of-everything level
OMFG 12 -
You reap what you sow I consider this the hardest level of the rank, even more than OMFG 20. I thought the hardest part was just getting two lemmings to use the bottom teleporter without anyone else dying to the water. Other than that, resources are extremely tight, so figuring out the solution can be quite difficult.
OMFG 13 -
Wasted Talent Tricky more than hard. Figuring out how to prevent lemmings from going into the trapped teleporter is not trivial, but it's not too exceedingly difficult either. I definitely don't like how the trap is very well-disguised in this tileset. Those other hanging down from the ceiling wiggly things can be mistaken for a trap as well. Luckily, there's only one trap in the exit area. I believe there is a level in Lemmings Plus Alpha with this exact same title, the penultimate level of the pack which I was stuck on the longest out of all the other levels in the pack. I wonder if namida must had taken inspiration from your level, since his pack came much later than Pit Lems.
OMFG 14 -
The sky is the limit Trickier repeat of WTF 18, although not much harder. Solution isn't as interesting as the one I used in WTF 18, just a slight variation. I just watched my replay for WTF 18, and the solution relies on the solid ceiling. So, I either knew about it before WTF 18 (most likely, since I'm certain I rediscovered it in Paralems) or WTF 18 was the one that taught me about the solid ceiling in Old Formats. Yet, it's really interesting how the solid ceiling completely escaped me on OMFG 20 even though a solution that uses it was just a rank ago! Oops.

OMFG 15 -
Icing on the Cake This level managed to stump me for a bit before I realized that I wasn't thinking about the solution the right way. Nice looking level with a good solution. I like how you used the slowfreeze for the icing.
OMFG 16 -
That's the name of the game I feel like I played a level very similar to this in another pack, where the entire level was the word LEMMINGS spelled out, so nothing too special other than being an easy 15-of-everything level. I don't remember where it came from, though.
OMFG 17 -
Man Shields Nice puzzle involving releasing the zombies to trigger off the traps before you can work on saving the crowd. I didn't have to release the last zombie on the right, and I also have several skills leftover. I used a builder and a platformer to bypass the radiation trap.
OMFG 18 -
Ramp up your lemmings I also consider this a pointless repeat. Really the only difference is using a combination of stoners and stackers to get up, and I'm definitely familiar with it from Icho's NL Tutorial Pack, so it was easy. For others, it can be a difficult level if one doesn't know about it.
OMFG 19 -
Builder buddies Short and very easy, given that it's supposed to teach another trick of using builders to turn around when there's no solid terrain. I can still see how this level can be difficult for the less experienced players though. For one thing, it requires the right RR. For another, it requires making the second builder build in a precise location, specifically, the moment it steps off of the first builder's first brick.
OMFG 20 -
Cherry Picking As I already mentioned in my previous post, this level is completely 100% fair IMO, as I was very well aware of the solid ceiling from a previous level in the previous rank or from some level in Paralems. Here, it somehow never occurred to me to use the solid ceiling even though the last time I used it in the solution was from the previous rank, WTF. Oops. So, I guess it was simply a reminder from you that I was able to figure out for myself, which means you didn't give away any of the solution. I can see that now. This is what I appreciate IF I ask for a hint, where I prefer pack authors give me one that doesn't give a major part of the solution away. At the same time, you now know that unless I specifically request a hint, me stating that I'm stuck on a level DOESN'T automatically mean that I'm asking for a hint

I'm Not to mention that for some reason I didn't think it would work with just two stackers. It definitely should had been obvious to me that using the digger after giving a left-facing lemming a climber would just lead to a dead end, but I never made the connection.
In any case, not a hard level at all. This reminds me of a United level that required a certain trick that I had never ever seen before that would had been impossible for me otherwise. Icho's hint to me was that he learned it from Wafflem, so since the level completely requires it 100%, I decided to take the time to play Wafflem's pack. Once I made the connection with the Wafflem level where I've seen it, I came back to the United level that held me back and it was an auto solve. What isn't certain is whether or not I would had figured it out given enough time. As for the solid ceiling for OMFG 20, it probably would had come to me sooner or later.