Hi! Is it OK to submit a not-finished entry? In my case, it may lack some art but would be fully written and playable. 

Also... Is it OK to charge for it? I could provide a link for the judges to get it for free.

Feel free to submit your unfinished project, specially if it's only art that's missing but I would call it an Ashcan Edition if it was me.

And of course you can sell your product! It's your property after all!