Warning: Do not download from third-party "download manager" sites. They often bundle malware or outdated versions. Always use official Microsoft sources.
Yes. Use DISM to mount your Windows image (install.wim) and add the feature offline. That way, every new PC gets it pre-installed. Warning: Do not download from third-party "download manager"
This method never touches the internet.
This indicates that your system's internal files are damaged. If you prefer the PowerShell interface over Command
This happens if you forget the /LimitAccess switch in the DISM command. Windows tries to go online, fails, and aborts. Re-run the command ensuring /LimitAccess is included to force the offline behavior. Warning: Do not download from third-party "download manager"
If you prefer the PowerShell interface over Command Prompt, the logic is similar to Method 1.
DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:D:\sources\sxs
(Replace D: with your mounted ISO drive letter)