I would say no and yes.
In the rules for this jam,
"Once that countdown is done, you will not be able to edit your submissions any further. It is recommended that you upload your project at least 2 hours before the deadline. This is wiggle room to catch and fix last minute touches. There will be late tickets available on request if your game has game breaking bugs that need repair".
I would think altering game files is a big no no, but to fix a typo in the title or to add more in the description seems fine to me.
If you are interested in fixing up the game files, like releasing "Game Jam Game 2.0", then you should wait a couple of days after the jam had ended and then label 2.0 as a "Post Jam Version" for clarity. Hope this helps.