Far from guaranteed, but a ton of Xbox games are cross platform now. Afaik a few years ago they promised that all first party titles would be cross-platform with Windows.

With that said, there’s occasionally caveats to the Windows store versions of those games. The obvious example is that Windows store version of most Bethesda games is drastically inferior to the Steam version of them because the script extender that pretty much all but the simpler mods require doesn’t support the Windows store version of those games.

IIrc they’re called Xbox Play Anywhere titles.

No, though it is much more common recently.