You can, though. Or at least could. Buying media and books etc used to be a way to throw some money at a distributor and get something tangible in return. There's probably still some available. Alternatively, you can probably donate.
But a nice part of the first software freedom is that you don't need anyone's permission or license to run Free Software.
Yes. Good filters and privacy/security are an absolutely vital requirement today. Unbreaking things and adding features via extensions or something are also good.
I really don't remember. I know Creepshow must be one of the oldest ones and Tales from the Crypt. Jaws might be, too. And the 50's version of The Fly and Asphyx are old ones but I can't remember when I've seen those myself. Long enough ago to not remember. Let's say under 10 anyway, most likely.
Windows systems do indeed have a long history of cannot.