Hello JaN, my apologies for the delay. This year got so crazy that I forgot about the jam, BUT let's not quit so soon ;)
I really like experimentation, so any commitment is allowed: unfinished works, tests, finished games, re-submissions. Feel free and do what makes you happy.
Concerning plots, storylines, etc., same answer. Do as you please, as it makes you feel fulfilled with your work!
And again, SORRY for the delay.