No troubles at all!
1- there's been fan entries in the past, as long as you reference clearly in your credits, you should be ok (it's not rule breaking for us anyway)
2- yup, it's fine! But if you want your entry to be archived at the IFArchive, we'll need a downloadable copy (if you don't want it downloadable on itch, you can reach out to one of the organisers directly on Discord/email and we'll handle the rest :) )