Edit Privacy page to control options available


Well-known member
At the top of the user's Privacy page we have

X Show your online status
This will allow other people to see what page you are currently viewing.
X Receive site mailings
You will receive a copy of emails sent by the administrator to all members of the site.

I want this NOT to be visible, and for both options to be selected.

Below "People who may ..." there are 5 tickboxes.

How do I make it so you cannot untick them?
So you can only select an option, but not opt out.

Thank you.