P.S. Just play and enjoy. And if someone wants to go through the game more meticulously, that's their personal right.

That's what I did.
And my discussions are nothing more than expressing opinions...

1. Not everyone can, for various reasons, sit at the computer for 10 hours straight, but only 2 hours at a time. How do you determine how many hours someone plays?

Well, firstly, you have to look for a map that takes 10 hours to complete. And secondly, a tournament isn't a one-day event... you can choose a time when you're free to complete the map almost without interruption.
And thirdly, why take everything so literally?! Let's say it took 8 hours to complete the "Tester" map. We set the completion time to 15-16 hours, or even 24, whatever.

2. The organizer must send a save to each participant at a certain time, make sure that they have completed it properly, be in touch exactly 10 hours later to receive the return save, and do this with each participant registered for the tournament.

What's so complicated about that?
The time for accepting applications for the tournament is agreed upon, for example, from 21:00 to 22:00 daily.
I log in and submit an application when I know I'll be free. The Organizer sends me a map... everything else follows. After 24 hours, I must send him the final save... If there are problems with the internet or something else, or the save is corrupted, the information about the file is saved - size, creation date, etc. - and so on... it becomes problematic to falsify.

P.S. Everything is much more complicated than it seems, but it's much easier than you think...©