I feel like there should be a comprehensive list somewhere with all the rules (about judging, submitting, hacking etc), something that describes the entire process of a contest with all cases that can occur. A "codeforces handbook" if you will.

Story time: I've had a situation in the last contest I've taken part in, in which I have solved the first 4 problems in the first hour of the contest. For the last minutes of the contest I was starting to get bored (I had absolutely no idea how to solve the last problem and I've already been through all the submissions in my room for hacks). I started to modify my code for the 4th problem with different seeds and parameters (it was a randomized, heuristic solution, as was the official one) to see how it fared. I wanted to see how the new parameters would fare on the official tests, so I started to search google and codeforces blogs to see what happens if you re-submit after you've already passed the pretests and no matter what search terms I used I couldn't find anything on the topic. Ultimately, I decided to submit since in pretty much every contest I've taken part in if you've got "Accepted" on one solution, the submissions after the "Accepted" do not matter towards the score. But lo and behold, there was a penalty! My first solution got "Skipped" and only the last one was evaluated, adding more than 1 hour of submission time and losing me 300-400 points. I was stunned, left to wonder why in the world this isn't documented anywhere on codeforces. Only after the fact did I managed to find something about it, by googling "Codeforces skipped submissions". The whole situations seems kinda silly to me.

To avoid situations like that in the future, maybe it wouldn't be bad to have a centralized handbook with all the rules (or maybe there is one and I am missing it?). I remember how confused I was about the whole "hacking" system as well when I started out (nowhere was it clearly explained what a "hack" was or the concept of rooms or locking problems).