Is there a way to check the MyBB version from the files? I'm in a weird situation that I need to fix to be able to upgrade, and I cannot access my Admin panel.
I dont think so, but if you have a corrupted upgrade you can follow thes steps:
1) Download the latest version again
2) Set inc/config.php's database information to the correct information
3) Set cookie settings and your board url to the right settings in inc/settings.php
4) Upload the files by FTP
5) Run the upgrade script.
Hopefully that will work! The only problem is you may have to redo stuff like tempkate/theme changes, but atleast all your posts, threads, and forums are still intact.