If I have several MikTeX's distributions on my Win 8, which one is chosen by WinEdt 9.0? See also my question here. There is stated that WinEdt chooses one automatically.
Do you really have several versions of MiKTeX on your computer? How did you?
I think there is a missunderstanding: You can only install one MiKTeX version on Windows, because the installer of MiKTeX uses always the same directory(s) depending on user or admin installation. It could be (I never tried it) to use the mobile version of MiKTeX contained on a usb stick resulting to be used with an different path
E:\... instead the usual
C:\.... But then be very careful, that the both versions are not mixed by using different pathes to both versions (for example which pathes are used in the editor you use (you have to use different one to use different pathes to reach the correct tex version) to create tex code, or is the standard path used leading to the installed version?). At last it is not a very good idea. Better omit it.
With TeXLive it is possible to have several versions installed on one computer. To change the used version there has a path to be changed, which one I do not know, I'm only a MiKTeX user ...