

It’s surprisingly simple, if you have two cameras side by side, you’re capturing two images where the camera is moved horizontally relative to the subject. If you now instead take two pictures where you move the subject horizontally relative to the camera, you’re achieving the same effect on the subject in the images. This means you won’t get a correct effect on every video, and the background will be unaffected, but it can work.

Not sure what you mean by that, but off the top of my head, you can get certificates via challenges that prove DNS control (rather than checking if the DNS points to your server), and you can get wildcard certificates so you don’t even have to expose the existence of subdomains.
And that’s ignoring the option of using your own CA, which only really works with your own devices, but for local access might be viable.