I was wondering how to protect my account from being modified by other admins. I know it's possible as my predecessor as done so with his, but he didn't tell me how to do that before he disappeared.
you can add your admin account to super administrators through ./inc/config.php file
around line 70 of config.php file find code like $config['super_admins'] = '1';
1 in above code is the super admin user ID (who installed MyBB forum)
you can replace it with your user ID - or add your user ID with a comma after that 1