"Accidentally hurt ourselves on accident"
I'll answer those questions for you, Sora, because I have nothing better to do and because this guy is funny.
To answer #1... Yes you can grab. Why wouldn't you? However I'm going to assume that in a skill perspective when evaluating a replay, the guy who grabs is going to make a lot less of an impressive first impression whereas the guy who does the same things that the other guy had to grab to do but now does them without grabbing is obviously going to be better rewarded at the end of the day. This is just my opinion but it IS shared by most people who still parkour nowadays. Grabbing is perhaps the most looked down thing in a parkour replay and instantly marks you as a complete noob so the key aspect when doing parkour is to learn how to climb and move around without grabbing.
As for #2, I think that you can be a big boy and figure out how to edit the replay before your little "accident" to prevent it and as said before, you're aloud to do it but it makes you look less skilled than you actually are UNLESS you do it on purpose to do something cool. In that case go right ahead.
Cheers.