If clr isnt enabled some programms will just use whatever net is awailible, they may say net4.6 or greater, for example. It all depends on the programs author and everyone uses different prrograms, you will literally have to test your programs out for yourself.
On w7 and 8.1 i smack every damn .net into an install as i can, on XP i used every damn .net addon, from 2 to 4.
Read this post on capturing an image and you can see ive put in every damn .net i could because i dont want to run into problems later and i must have net3.5 installed for 1 programs i have to use, there is no other program i can use. I wouldnt put all those nets in if i didnt have to.