microsoft-windows-netfx3-ondemand-package.cab is the offline installer for .NET Framework 3.5
Q: Can I use this to install .NET 3.5 on Windows 7?
No. Windows 7 has native .NET 3.5.1; this .cab is for Windows 10 and 11 only. Download Microsoft-windows-netfx3-ondemand-package.cab
(On Windows Server, use Get-WindowsOptionalFeature -Online -FeatureName NetFx3) microsoft-windows-netfx3-ondemand-package
Q: Do I need to uninstall it later?
Usually not. But if you must: dism /online /remove-package /packagepath:... Download Microsoft-windows-netfx3-ondemand-package.cab