I found a silly little bug which broke most of the game would I be able to fix it?

No, you are not, at least not be able to submit it. It will be judged in the state you submitted (functionality is a point there too).
But most games will have more or less bugs ;)

Is there a way to update it somehow or does it go against the rules?

it is not possible during the judgement phase, and also gainst the rules. 
Then there would be no need of an end date in the beginning. :)

is there a discord?

My game https://lolmanbruh.itch.io/flappy-birds please if u could add it also the Repo