Updating the situation:
I’d like to do the following: for the first 15 minutes, I want to play the video normally and then either not show the rest or display a frozen image instead.
I occasionally encounter corrupted videos that only show certain parts and not the entire content.
I was wondering if I could replicate such a situation based on my selection. However, I would also like the option to view the entire video normally if I choose to do so through an alternative method
You could use Ruffle since its an emulator for Flash:
https://en.m.wikipedia.org/wiki/Ruffle_(software)
https://github.com/ruffle-rs/ruffle
Websites like HomestarRunner use this so you can still experience the site as it was intended.