Here:
https://social.msdn.microsoft.com/Forums/en-US/4e2fce2d-f08f-49fd-a2f7-60822a58e4eb/can-net-40-45-or-461-all-be-installed-on-one-machine
The answer said installing 4.6 would block 4.5 and 4.0 as it includes them.
I'm having a problem with an app that wants to install 4.0, but when it runs, it gets an error saying it won't allow a downgrade from 4.5 -> 4.0. That's fine -- except then the application won't continue the install. So if 4.0 is in 4.5 and they are in 4.6, why do applications insist on rerunning a .net installer that will fail. It's more than a bit frustrating -- especially since I ran into something like 5-6 installers recently (past couple of days) that force me to rerun either a 4.0 or 4.5 installer -- when supposedly 4.5 is already installed. The installer doesn't return positive results when .net is already supposedly installed.