Installing .Net Framework 3.5 on Windows 8.1 and 10 is only through Programs and Features in Control Panel. But if the computer is configured to get the windows updates through WSUS, installing through Control Panel will most likely fail, no matter what else you try.
There is a Group Policy setting that you can alter to bypass getting the updates through WSUS.
Open Group Policy Editor (local or in AD), go to Computer Configuration → Policies → Administrative Templates → System, and open a setting called Specify settings for optional component installation… on the right-side panel.
Then select Enabled, and check the option “Contact Windows Update directly to download repair content instead of WSUS”
Click OK and done. Run “gpupdate /force” to update the changes on the workstations to avoid the reboot.