at the end of the jam the community votes should start for 3 days that will give us the 10 community winners and after the end of the community votes the judges will votes for the official 5 winners, I'm not sure about the others 

I always submit early and update a few times as I progress as I have entered some and life has got in the way and I couldn't enter.

I would rather have something entered even if its not working but show the concept.

As RicoTV said, submit as early as you can, and update your game page with new version of your game as you go.

That way, if things go wrong, you don't need to stress as much, because you submitted "something" to the jam. (Even if it's not as good as you hoped it would be.)