Qustions about .Net framework

[weixin_38048892]

Q1: .Net Framework4.0 environment is required when running WPF applications in win7 or XP. Is there any tool to detect the environment to ensure that WPF applications will work properly?

Q2: .Net Framework4.0 environment can’t be installed in some operating system. Is there any solution for error codes?

Q3: In Win10, how can I uninstall the original .Net framework and install .Net framewok4.0 which is lower? Can you provide a framework clean tool?

Thank you!