Ball Pit: Intended solution. There's a backroute, though (finlay found it a while back), but I doubt I'll bother to fix it.
City of Satan: Backrouted
hard, but my intended solution reeks of backroute (depends on some rather tricky timing) so I don't have much of a problem with backroutes here. I might move that chain, though.
Crystal Village: Oh wow, that's an embarrassing backroute. I'm definitely going to fix that.
Lem Dunk: Close enough; I made that when I was like 12, so the intended solution has been long forgotten and even I solve it a different way each time. The bit with the diggers in the pillar under the entrances was clever, although the digging on the bricks at the bottom was part of one of my solutions. And you don't need to dig to build to the exit.
Prison Break: Oh, for the... I guess this is what I get for not knowing any glitches. I doubt I'll fix that one, especially since that part should be easy enough to figure out without glitches anyway.
The Crusher: Close to intended.
The Great Outdoors: The most tedious intended solutions get the worst backroutes. Another one that I'll definitely fix.
The Limit: Pretty close to the intended solution. (I will also admit that I really don't like this level, and if I redo the pack, I'll probably nuke it.)
Unidentified Lemming Object: Good thing I have another puzzle in here, because I'd feel like even more of an idiot for leaving in a way to backroute around the originally intended puzzle. Although, come to think of it, I really don't think there's a way to pull off the intended puzzle without a backroute at all. Also, it's possible to get 98%.
With All Deliberate Speed: Better than the intended solution, although I might take it out anyway.
So yeah, you backrouted six of them, and I know of a backroute for one more. As if it weren't already obvious enough that I'm really bad at this game.
Some attempts at fixing backroutes:
CRYSTAL2.LVL = Crystal Village
GRASS2.LVL = The Great Outdoors
HELL2.LVL = With All Deliberate Speed