0318 - It's not exactly a back route, you just found a very clever alternate solution. If you take what you did and perhaps reverse it so that everything destruction wise is going in the other direction then that would give you the intended solution. I think this is why you had precision problems, because you tried to brute force a solution which is more or less the same, just in a different direction.
0319 - This looks ok to me, this is Wafflem's solution to a level which I made so he has the final say on whether this is acceptable. This level was originally in the Murder rank but it slowly got pushed down the ranks after feedback. I suppose it could get pushed in the other direction again.
0320 - Very nice solution here

. There are many ways to go about this level but I think it's safe to say all of the platformers and builders are needed crucially in all solutions.
0401 - This beat The Legend of Ray Beeston in LOTY sadly, I can't change that

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0402 - Ok, the problem here is I have already edited the Star Light tileset and your first replay doesn't solve so I was not able to see the back route entirely. From what I could see it was obviously a back route anyway because you were going in completely the wrong direction. From what I could make out from your 2nd replay (15_52), that one looks intended.
I guess that means that your back route is already technically fixed but nonetheless well done on finding it, I guess that is back route no 1 in this pack.