So, I did a run in any% glitchless, and when I checked through the categories, I noticed there is a category called 100% glitchless. And I just have a few questions regarding the differences between the categories, and a few specifics.

So, In 100% glitchless, what exactly qualifies as 100%? Do you need to get all achievements? Secondly, Can a single run be submitted into multiple categories?

All of the tests must be completed for it to be 100%. You can submit a single run into multiple categories if you want.