I wanted clarification about this, since the rules didn't mention it.

Going into browser's castle after you already beat the first browser phase makes kamek do a shorter animation to make browser big.

In an individual level run of browser's castle, is it legal to use this shorter animation rather than the standard one you get on your first visit?

It is legal to utilize the shorter cutscene due to a death, as long as you include the death in the overall IL timing. Same goes for using a super guide block as a platform.

Thank you.

One more question that is unrelated, but I don't want to make a new thread.

I'm new to speedrunnig, so any video I make would be of atrocious quality. That isn't a problem, right? For a timer, is it fine to edit one in the video afterwards, or do I need it running live with the run?

You can edit it in afterwards, as long as the time of the run is correct in the submission it doesn't matter