Sure, open the Run box and type winver
If I were you, I'd do some searching in the MCE sub-forum. I faintly remember something about some files showing lower versions after MCE was upgraded to Service Pack 3, something like version 3.0 with SP2 / version 2.8 with SP3.
I am curious which one of these files may start the application install
I'm afraid you can't just double-click a file and hope for the best. If the .NET services are started and running after install, the application should be aware of the presence of .NET Framework on the system.
I have Windows installer ver 3.1 and 4.5
You can have them both as install files, but only one on a running (live) system. But I'm pretty sure anyone, if installed, should do the trick. If in doubt, install v.4.5.