In retrospect it's a miracle that I managed to restore @CHT
's site. He'll be able to view his blog, and maybe add pages and posts, but he won't be able to load plugins or themes. or update his plugins and themes. Which is going to be a real problem since the backup is quite old.
Since the above restoration of CHT's blog, I checked up on my own WordPress sites, and when I tried to update the plugins of my WP sites discovered that we don't have any author privileges to be able to upload or update themes or plugins. Something is genuinely weird with our author privileges. I tried to do it with the FTP option and that didn't want to work either.
Later on I tried to do things manually through the File Manager but that had issues too. Like exactly the way CHT had said. When I changed the folder privileges to 777, something in the system keeps on resetting back to 755 - like there's a default for the folder privileges that we're unable to change.
Towards the end of my checking it got doubly weird. Like I deleted an add on domain folder in File Manager and when I refreshed the File Manager, the folder was still there. I went a step further and deleted the add on domain as well. The Add on Domain deletion worked. But the File Manager folder for the add on domain was still there. I deleted it again, but it wouldn't go away. I then thought to take a break.
Looks like we don't have any privileges to change folder privileges.