How to revert chown command? If I run: sudo chown -R user:user / Can I revert it to what it was before I ran it?

In short: no.

You'll need to restore from a backup. (Some backup tools might have options to only restore permission, others can list backed-up files with their permissions and you can use that to fix your system.)

If you don't have a backup, you'll need to fix all that manually.