In addition to hardcore mode for locking down preferences while a session is running, Focus can also lock preferences entirely. This is useful for parental controls or if you have a trusted friend who can set the password when you need the extra push.
Preferences > General and check Password mode. Enter the password twice to confirm the change, and you'll be immediately prompted with a locked preference panel. Now to make any changes to the preference panel, you'll first have to enter a password.