Suggestions for Dealing with Prohibitory Symbol

[kat.hayes]

My iMac Pro would not open photos on the desktop, so I rebooted and it displayed the Prohibitory Symbol. I have not updated it, and have no idea why this may have occurred. I plan to follow the steps on https://support.apple.com/en-us/HT210901 though I have a few questions first:

1. I last backed up two days ago, though I just happened to have spent like TEN hours sorting through photos from external drives and placing them onto the desktop. Is there anyway to get access to my desktop temporarily to back these files up before I follow the steps on that page? I still have the files on the external drives, though it hurts to think about the time I will need to spend going back and doing it again.

2. I accessed my iMac remotely on my network from my MBP to sort through some of these files yesterday, is it possible doing this caused this in some way?

3. After following the steps on the support page, and assuming everything boots back up again, how can I know that there are no corrupted files that may cause a problem in the future? I am referring to both system files as well as media, photos and videos that I do not want to risk losing.

Thanks for any info!

 

[kat.hayes]

Update: I ran Disk Repair and nothing seemed to show up, it just showed "Operation Successfull" I tried to reinstall the OS but it wouldn't let me because it indicated there was no internet connection. I tried multiple times.
So, I rebooted and I now have access to my desktop, and I am copying the files that I was concerned about to an external drive.

What do I do now? Is the OS ok? I don't want to back it up with Time Machine in case there are corrupted files. I would like to make sure somehow that everything is back to normal before I start working on it again.


Thanks