But isn’t it available only for Windows/macOS?

Really? Do you have any source on that?

If it’s true, I bet it’s only if they’re actually running without ever spinning down.

Exactly, you can just redownload them later. But pay attention if you have rare Linux ISOs, maybe because of their quality or if they’re in a specific language.

MySQL has been the “default” choice for a long time for PHP programmers. I don’t know why.