How to put on Windows 8.1 NET Framework 4.0?

Question

Software and Internet Services

Bottom line: I work with software for full-fledged work that needs Framework 4.0, to install it, if I understand correctly, you need to demolish NET Framework 4.6 (which, judging by the version detector program, is installed with an Unknown build: 394271 error).
It is not in the uninstallation of programs
NET Framework Cleanup Tool does not plow

Answer 1

net framework is a system component.
In "Add/Remove Programs" run "Turn windows features on or off" and uncheck the boxes.
you can do the same via powershell:

Get-WindowsOptionalFeature -Online | Where {$_.FeatureName -like "NetFx4*" -and $_.State -eq "Enabled"}

- for check.
And add | Disable-WindowsOptionalFeature
to remove.
then put the 4th
judging by https://msdn.microsoft.com/ru-ru/library/5a4x27ek(...
there are no restrictions on the OS, respectively, according to the article, go through what you need to install for normal operation.