Before I ask the question, I believe the answer is no, but since I have very limited understanding of how all this works I'm interested in the facts others can dig up.
The question, then:
1) Can a computer running Windows XP Pro 32bit, with a directx10 and 11 supporting video card, run a directx11 supported game in directx11?
2) If not, then is it true that only among Windows Vista and 7 versions, Directx10 can be the version used by games that support it (as long as a directx10 video card is part of the system?) And then, also, Vista will be upgradable to directx11...and so with a directx11 video card and the update, both Vista and 7 will support directx11 games?
3) Perhaps the overall question from me is... In order to utilize directx10 or 11 functionality in games supporting them, the Windows version I use must also be able to support directx10 or 11?
Thats correct. Due to a change in how drivers work in Vista/Win7 compared to WinXP, only Vista and up support DX10 and beyond. While you can install and use DX11 hardware in XP, you do not get the advanced features, and the games will run in DX9.