Windows Update Fails and missing registry keys

I have windows 10 Home edition, 1607 version (14393.321 build) and lately my computer has been trying to update to 1703 version but fails. I've tried the usual stuff like troubleshooter, clean boot, system restore.

The error code is 0x8007001f.

Then I tried to reset my computer, which failed so I saw a solution about running a sfc, which failed with the message: "windows resource protection could not perform the requested operation".

All these led me to the following post: https://answers.microsoft.com/en-us/windows/forum/windows_vista-system/windows-modules-installer-error126/2a45788d-c1e5-4b62-a5b1-2410cbcbf813?auth=1 and the first answer by "theholycow" (yes I know, it's from 2011 but bear with me) which suggests that there is a registry key missing HKLM\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\Version

This key indeed is missing from my computer, but when I navigate to C:\Windows\Servicing\Version to see what key needs to be added, I have 3 subfolders inside:

The first two are empty, the third is not.

So first of all, what key do I have to add, if any? Second, will this fix my problem? Do I have to format my pc? Why does reset fail?

I tried adding the key with .349 at the end but sfc still fails. Any suggestions?

After having updates repeatedly fail on a number of different PC's, I find it's easiest to download the entire ISO for Windows 10, use the Windows Media Creation tool to create a USB boot drive, and do an upgrade from it. It is far more reliable than the Windows Update patch process, and usually faster, too. Be sure to select Keep personal files and apps, though it's a very good idea to image the disk first, in case something goes wrong.

Regrettably, this doesn't determine what issue(s) caused the update failure, but I am not confident a Windows Vista issue prevents a Window 10 update, as you suggest.