Windows 10 - Post-Update Black Screen (No Boot)

Hello there, I've had an issue with my Windows 10 on my PC since yesterday at around 7pm EST.

I came home from work, and my PC was sitting on the Desktop, as per usual, I could access my files, browse, play games, ETC, and there were no issues, but I wanted to restart my PC as I do from time to time, and the only options I had were to "Update and Shut Down" or "Update and Restart", so I pressed "Update and Restart" and didn't think anything of it.

I came back a little while later, and Windows was stuck on the Spinning Circle, which was odd, and it was stuck on that for about a half hour, and at that point I figured something was wrong, and restarted the PC.
Ever since then, whenever I restart my PC, my BIOS loads in and I can mess around with that, change clock speeds, Boot Devices, ETC, and everything is fine and normal for standard boot until it tries to boot to Windows 10, in which the BIOS screen ends, and a Black Screen begins, which doesn't go away until I restart the PC, which once again loads the BIOS and then black screen, and it doesn't ever actually go back to even the Spinning Circles at all, and I can't access any kind of Windows Repair, or Safe Mode, or Recovery, nothing.

I looked it up to find similar issues, and apparently at the beginning of the month there was a corrupted Windows 10 October update which was causing issues such as this, (although that was at the beginning of the month and supposedly was fixed), and suggested I call Microsoft, and so I did.

We tried Hard Booting, Holding the Power Button down for 1 then 2 Minutes, and then after being on hold he determined I should wait until the next day and get a call from support with a more suitable Assistant.

The next day rolls around and I get the call, and after explaining the issue as best I can to him, he determines that its a Hardware issue since it wont even access Windows 10, and that it just needs replacing.

It isn't particularly a new Motherboard, but I've been using my PC with minimal issues for 5 years now, custom built mostly by me, started with Windows 7 Pro and updated to 10 Pro when it released, I've upgraded the PSU, GPUs, RAM, the Hard Drives and Reinstalled Windows 10 before without issues I couldn't figure out until now. First off, I can get into the BIOS and mess around with it which makes me believe it might not be the motherboard, although I am not ruling it out, especially given my second reason.

I refused to give up and decided to try and run Windows 10 on a Flash Drive, using the Official Media Creation Tool to create a Windows ISO, and installed it using WinToUSB, in order to try and boot using an external device with Windows 10, maybe get some of my more important files off, ETC, but mostly to get access to my Hard Drive to possibly try to repair the issue somehow if I can find a tool to do so, or even Reinstall windows again on my Hard Drive to start anew, I'm not very knowledgeable of drivers and software.

At first, after the BIOS it was able to start the Windows Logo with the Spinning Circles, before cutting back into the Black Screen and sitting there, which worried me, but after restarting the PC and trying to Bott it again, I was able to boot into the Flash Drive, and run the setup for Windows 10, so the capability to load into Windows is there still, as it can get past the BIOS into Windows, and after allowing the setup to run, I'm in a working, although extremely slow, build of Windows 10 Pro.

What happened, was it for sure the update or might there be something i'm missing that might have caused this? Is there anything I can do from here to repair Windows 10 Update through a Tool, Windows, Windows Update, or should I just reinstall Windows? I'm not sure where to go from here, and any assistance would be appreciated.

EDIT: I also should have noted that after boot, I am not able to see my Hard Drives, which is odd. I would understand my C: Drive not showing up, but all 3 of my previously completely working hard drives? I find that hard to believe.

Also, whenever I hit My PC in order to try to view my Hard Drives, going through Folders is fine but if I hit My PC to try and look and see if my Hard Drives show up, the PC slows down to a half for a moment, and then extremely slowly loads for a minute or two before loading and showing the only Storage Device as my CD Drive and my Flash Drive as the C: Drive; even after restarting the PC and are-Booting to the Flash Drive, which Boots Windows up normally.

EDIT 2: After opening up the Hard Disk Partitioner, I was able to see all my available Hard Drives, and set them to “Online”, as they were set to be “Offline by Adminstrator Policy”? I don’t recall doing that, but now I can access my files on the Hard Drives, but the same questions remain

Welcome to tenforums.

First, a useful tool - a live boot disk with many utilities:
Windows 10 Recovery Tools - Bootable Rescue Disk - Windows 10 Forums

As you'll see there are utilities support checking disks, partition manager, data recovery etc etc, so you can verify your disks and read them and copy anything accessible.

Second, do you use disk imaging routinely as we so often advocate? If so, you can simply restore a previously created disk image, and assuming no hardware problem, have your PC running as it was when you created the image (e.g. Macrium Reflect (free) + large enough external storage for disk image sets).

Third, if you don't, but have appropriate backups of data, and a clean install is not too arduous, a clean install would be the most straightforward approach, preceded by a disk check.

The problem presently is of which build. I use 1709, some are struggling with issues related to file associations with 1803 and one particular update, whilst 1809 (released, then withdrawn after major issues were identified).

Windows updates and upgrades should be regarded as potentially detrimental and hazardous, and treated appropriately. (Disk imaging...).

You have Pro, so you can set updates to Notify and feature updates (upgrades) to Deferred for up to 365 days.
You also have Active Hours in Settings to protect against unexpected restarts.
There are more options.

I would recommend using these, as I do, to give you control of updates etc.

Other approaches:
It is possible to reverse pending changes using an offline DISM command.
You can run SFC /SCANNOW using the offline version.

Basically you can spend perhaps a couple of days trying to get your system rebooting... or clean install.