since you're allowed to do runs from a completed file are you allowed to do the K Level anywhere in the run or do you still have to do it after you collect all of the KONG letters in the world you're running

I think doing the K level after the normal ones was intended when the rules were written, but the categories are so underplayed that I doubt it would matter much if you did the K levels earlier (that is to say, the rules would be adapted if enough people decided to do K levels early). I personally prefer doing K levels at the end in IW practice (mostly because it's more relevant to the full run), but yeah you could go either way