Is 2.8 limited to Windows 10? I have both windows 10 and 8.1 my machines.
No, It should be able to run on anything that will run OpenGL 3.3, I think, so any OS/hardware that can run that should be able to run 2.8. Now.. the older you have, the more likely you might have issues, and some features might not run optimally, but you should be able to at least run Blender.