What it says on the tin.
Assume that every easily-googled effort to fix Windows 10 has failed and rollback attempts have failed.
Assume I have access to a PE/LiveCD.
Assume that Power -> Shift+Restart -> Troubleshoot ->??? is useless to me.
(This is quite a unique situation!)
Assume that I still have the Windows.old file.
Assume that I really don't want to reinstall from scratch.
With these assumptions in mind, how do I MANUALLY rollback to Windows?