Welcome to my level topic! I've been making custom levels for longer than I can remember, but the first time I released a level was in 2015, even with levels I've released later with earlier dates. All of my levels can be downloaded from Marbleland. Feedback is always appreciated!
Usually I assume that one has the CLA MBP interiors downloaded already, but I will be happy to put up the file in a separate download link if you would like me to unless there's a reason I shouldn't or something like that...
First part, is I don't have a clue why it isn't working in 1.14, unless if it's because you need the textures of the levels I used.
Second part, how so is 1.50 not working? Does it not open? Does it crash randomly?
(05/07/21) Edit: This got a makeover, so the image isn't accurate to what the level is now. Thought I'd leave the the picture up there just for fun. This also ended up being my 27th level and is now ironically called Generic Ascent.