Hi! Your game is your own, so you can feel free to do whatever you want with it.
People will still see the game as part of the jam so if you're planning on doing something that makes it not 20-seconds long, it will look odd.
What people often do is keep a jam version and make a new version for the non-jam version. Or they keep a version in the downloads for the game marked 'jam version'. This really only applies if you plan on changing the game so that it no longer follows the 20 second jam rule because we don't mind if you start the game early or improve it later.
