I have a very limited knowledge of this stuff so I hope this explanation makes sense....
My parents have somehow got on my MacBook, and made it so that they can change any setting and view/modify my or their own internet traffic. They can achieve all this from upstairs. And their modifications aren't always "live", ie: modifications in real time.
Sometimes the screen 'glitches' and I see something that is non standard, ie: some web error flashes up on screen when I try to load a certain page, before reverting to the usual 404 not found page.
Oh and my 2016 MacBook Pro thinks it's up to date and it's running OS is 10.3.3
I believe all my internet traffic is being run through a homemade proxy which is how they achieve evil tyrant overlord status.
If someone could help me restore the MacBook to out of the box factory settings, whose installer verifies itself that it is authentic apple software by communicating with apple servers, I'd be very grateful.