Yes, I can confirm that I can compile the same project to 4.0 on win7 and run it on 2013 and 2015, and compile it to 4.5 and run it on 2015 on win7 (don't know how 4.5 acts on 2013)
However, I'm just curious if you will be able to disturibute this 4.5 project to other machines. I have some issues with that and I plan to deal with this later, when I find time. (I have fatal error on install. Not sure if it is related to 4.5, will deal with that later, right now im just curious).