What do you do when DNS is broken?
Fix it quickly, in case the secondary DNS breaks too.
You seem to be suffering from the delusion
Oh, FFS. The GP is simply mistaken, not deluded, you don't need to go all Shakespeare on him.
I can lock down android with a customized hosts file
You're on meth.
... uhmmm... personal recreation. I'm not sure whether prohibiting something like that is remotely legally enforceable.
Talk to the Catholics.
That's how it used to be.
And it's how it still is, except the memory manager handles it all transparently for you in the background, so you can simply mmap() in a file, which can even exceed your total physical RAM many times over, and the system takes care of reading / writing & mapping the pages to / from disk as necessary. All that's changed is transparent support for it in hardware and the amount of memory involved.