That would make Mint unstable. That is exactly what unstable means in Linux context. There are debian based rolling-release distros, including Debian Sid. This is one of the reasons people choose Arch, because it’s a rolling release you never have to worry about version.

There’s a good chance you might break stuff by upgrading major version like you fear, and that’s why it doesn’t happen automatically. That being said it should be safe, but good on you to prepare backups.

I usually give detailed responses, but honestly the correct response here is RTFM. The short answer is to install nvidia-580xx-dkms.

Arch wiki is such a great place that has the answer to most technical questions you might want to ask. I strongly dislike the idea that Arch is for advanced users, but it does expect you to read the documentation (which is why I dislike stuff like Manjaro that try to make Arch “accessible”, but end up leaving people in similar situations without even knowing where to look for the solution to their issues).

No, the problem with Windows 9 is that a lot of things compared the version with 9* as a catch all for windows 95 and 98, so they were worried with backwards compatibility.