There's no technical barrier to doing so. I uploaded new files to my project page and they also appeared on the submission page. This isn't just because it's my own game; there are a few other submissions with post-jam updates and alternate versions that show up in the submission pages for me as well. If you need my to, I'll take mine down, and I'm sure the other jammers will as well if they're not passed out exhausted, but it's an entirely voluntary/manual thing.
No, it's allowed. I just thought that option is usually locked by the system itself -- didn't know that it's unlocked by default. Because in some ranked jams I participated in, it was impossible to upload new versions during the rating period.
In that case then feel free to update it. Try updating it before Wednesday (or Tuesday evening if you live in Europe or the American continent)
