Access Forbidden to Public on shared hosting

Most likely a browser cache, run it in incognito.

I haven't tried to run CI4 without FollowSymlinks enabled, you can try to just comment that part out of the .htaccess file. Don't know what part of CI that actually needs that setting. There are no symbolic link in the application itself, to my knowledge. May be used by the tests.

If mod_rewrite requires it, then you need to access your urls with:
sub.domain.com/index.php/pages