Comments about levels:

-The lack of GADs really reduce the depth of the game's levels. Considering they're integral to the progression of many maps in the final, these early maps are more simple to beat.

-E1A5 and E1A6 are completely different, unrelated levels. The final E1A5 (2 Key Return) and E1A6 (Spring Surprise) are absent in the beta.

-E1A7 - There are way, way fewer missile weapons, so Darian is pretty difficult to defeat. In fact, the only missile weapons are in his room. It needs the oscuro key to enter, and the key is in there. You have to lure him out enough that he's not blocking the open door way and quickly get in before the door closes and without getting killed by his missile. You'll most likely take damage getting in there, but Thi Barrett can tank it. Maybe Lorelei can't.

-E2A2 - Unused, completely different level. The final's level, Great Halls of Fire, is absent in the beta.

-E2A5 - Way, way smaller and way simpler to beat. This level is like maybe 1/3 of the final's size, and nowhere near as mazey.

-E2AS - Overall easier due to the lack of verticality and far fewer enemies. One section involving fireball crossing can be intense though.

-E2A7 - Far fewer missile weapons and if you're not careful with missile weapon usage on the higher difficulties, you could soft lock yourself against Krist because of this. The boss room itself has no missile weapons, so you have to use the ones in that secret area enclosure; instead of a time delay door, it's just a simple push wall to get in. I don't exactly remember but I think there are just 2 bazookas in there, so on difficulty 4 that might not be enough; could be wrong though.

-E3A1's redundant secret exit to E3AS allows you to skip practically the whole episode straight to the NME boss after the secret level.

-E3A5 - There's a locked door required to enter to progress in the level. It's opened by a switch, but in this beta, these switches are single use only. So you have to run really quickly to make it on time. Just so you don't accidentally press it at the wrong time: It's in one of the "quilt pattern tile" rooms near the top, on a structure that has 2 of those flower turrets on either side. Do not press the switch to run for the door until you get the gold key.

-E3A6 - Way, way, way easier than the final because it is nearly devoid of enemies. The lead-up to the secret exit is way simpler too: shorter pit trap trail, no enforcer ambush at the secret exit and no god mode powerup. You don't need the powerup, though, as you can "swim" from pit to pit without taking any damage, as long as the player doesn't rise (heh) out of a pit.

-E3A7 (NME) - With the exception of some details like textures and enemy placement, the lead up to the fight is pretty similar. The boss battle area is quite different, though.

Way, way fewer spare bazookas, and it can start to cut close on difficulty 4. Only 1, compared to several, in the main boss battle area, and there is no ballistikraft room with extra bazookas. There are no ballistikraft rooms at all. There are still a few iron key door alcoves housing a bazooka each.

There is a health room, but it just has a small handful of monk meals in a small rectangle, as opposed to a large area full of priest porridges. The secret area behind the iron key full of priest porridge is still here though.

-E4A4 - There is no secret exit. Like E3A5, there's a single-use switch to a door essential for progress. It's early on, in the room that requires the iron key. The switch opens a nearby door to a little closet that houses the gold key.

-E4AS is warp-only, as there is no secret exit to it in any level. Beating this takes you back to E4A1. Good news is there are far, far fewer monks and it's considerably smaller than the final. Bad, bad news is there are practically no missile weapons; like maybe 2 or 3, with one being in a secret area. There are still enough monks to make this a major slog as a result. If you're pistol starting, there is an mp40 and it is pretty much a must; but it's also in a secret area.

-E4A6 - Unused, completely different level. The final's Circles of Fire is absent.

-E4A7 - Instead of waiting it out by dodging El Oscuro's attacks until he fleas as a snake, just hit the touch plate at the fire wall structure near the exit to move the pillar blocking its way. In fact, that's the only way to beat the level, as Oscuro turning to snake form doesn't move that pillar. This level is a good way to demonstrate how the snake heads have no collision with those pillars, so they simply clip through them.

-E4A10 is hilariously simple in geometry/layout for the Snake Oscuro fight. You start right in the boss arena, which is a much, much smaller area; and that's the whole map.

There are much fewer missile weapons, and they're located in only 2 enclosures (instead of the final's 4); also, there are far fewer fire pits and they're all spread out, mostly lone ones. Both of these make the boss fight way more challenging, although it is doable, even on a pistol start on difficulty 4. Keep in mind that you can kill the first 3 heads without needing the boss over any fire pit. There are also no eggs at all to destroy.

-There are none of the final's warp only levels at all (none of Dead In Two Seconds, Vomitorium, and This Causes An Error appear). However, this contains a big slew of its own set of warp-only levels, mostly test maps.

But one of the test maps is a full-blown map of its own, also cut from the final. it's called ROTT E2A3, but it's not The Room. When I originally played this map, the silver key was missing, so the level couldn't be completed without cheating. After making a comment about it back when this ROTT LE map conversion was released, it looks like this workshop item was updated to add the silver key in.

I'll add more comments later.

It's too bad none of the cut maps were thrown into the Reject Pack, or released in another way (for the original game release, not the LE, although that would have been really nice, too). Was probably more work than they cared for in order to clean them up for compatibility with the release build. However, it's kind of pointless that they didn't at least acknowledge the existence of them.

Maybe a request to throw these levels in, polished up or at least the broken one fixed, as official extra levels in the workshop?