Built-in apps fail to launch

Not sure which forum to post this in -- since it has to do with apps, trying here.
I'm at my wits end with my new Windows 10 laptop! The built-in apps (e.g., Connect, Feedback Hub, Microsoft Store, Movies & TV) show splash screens and then disappear after a couple seconds. Unfortunately, I can't say whether they've ever worked -- I've never tried to use them before!
With respect to the Microsoft Store app, I've gone through the wsreset.exe process -- the result is a dialog box titled "MS-Windows-Store:PurgeCaches" which states: "Windows cannot access the specified device, path, or file. You may not have the appropriate permissions to access this item." Of course, since Feedback Hub doesn't work either, I can't submit any.
I'm the sole user -- therefore administrator -- of this laptop. I show as having full control of the entire folder/file structure.
Looking at that app, I see it says: "Version 120001.1001.5.0, App 0 bytes, Data 0 bytes, Usage 0 bytes"
Similarly. looking at the Movies & TV app, I see: "Version 10.20011.10711.0, App 0 bytes, Data 16.0 KB, Usage 16.0 KB"
I tried resetting both of them -- no change in results.
Ran some of the "Get-AppxPackage..." seen in other posts command in PowerShell (opened as administrator) to reinstall all apps -- no change in results. However, there were numerous failure messages. Most said: "Cannot find path Program Files\WindowsApps\...." -- for good reason: there is no such folder! A few were "Deployment failed with HRESULT..."
I really Really REALLY don't want to reset the computer -- it's taken quite a while and trouble to get everything up and running smoothly!
Laptop is Toshiba Tecra A50-EC running W10 Pro v. 1909.
What else can/should I try?

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Supplemental: Found WindowsApps folder (at bottom of all the "Windows ..." folders). Found I did not have access; took ownership. Reran the "Get-AppxPackage..." command in PowerShell -- far fewer error messages, many more apparent successful recoveries. However, now, instead of a couple seconds, the splash screen shows and then is gone in an instant!

Downloaded W10 1909 ISO file, and both created a DVD and kept it on the desktop. Right-clicked file on desktop, but no "Mount" option. Was that what I was supposed to do?

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Well! Figured out how to "mount" ISO file. Performed Inplace Upgrade Repair Install. Now I've got numerous file/folder access problems -- can't even do a deletion of a supposedly corrupted recycle bin 'cause it needs administrator permission, even though my account is clearly identified as administrator. AND the apps still don't work!

OK: I've been seeking help from both Windows10Forums and here, and trying suggestions from both. I'm preparing this single response to provide to the people on both so both know what I've tried, and with what results.
1. No, I don't have a total disc image backup -- unless the full drive C:\ backups created using Norton Ghost 15 (yes, I know: ancient -- but works great!) count.
2. Added MS account using pre-existing outlook.com account, logged out of local account and back in with it -- no change in function of apps like Store, Movies & TV, etc.
3. Shut down completely and restarted, logging in using the MS account. No change.
4. Downloaded W10 1909 ISO, and "mounted" using instructions found online (PowerShell: "MountDiskimage -ImagePath..."). Used it to perform Inplace Upgrade Repair Install. No change in performance of the apps, but major issues trying to regain ownership of my computer (e.g., All Users, Program Data, WindowApps, etc.)
5. Decided to do a second InPlace Upgrade Repair Install. Unfortunately, I didn't think of the first one resetting power settings -- my laptop is connected to an external monitor, and stays closed itself. So, in the middle of the install, it went to sleep. When I woke it up, I had a black screen with a working cursor.
6. Got running again by shutting down and restarting the computer with the W10 install disc in the drive. Was told noticed I had an install in progress; did I want to continue?
7. Finished it, and, as evidenced by this, have some functionality back. However, I can't access my own Start Menu, even though the Security tab shows me with full control. Also, I keep being notified the Recycle Bin is corrupted -- do I want to empty it. But I'm told I need administrator permission to delete a particular folder, even though, again, I show as having full control in the Security tab. And restart gets me the sign-in screen for about 15 seconds, then the black screen with the cursor for about five minutes, and then my desktop.
8. Yes, I have attempted to regain control over folders I feel entitled to see, like my own Start menu!
9. Downloaded Tweaking.com Window repair tool and tried to install -- nothing happens on double-clicking -- no in-process indicator -- nothing. Tried opening as administrator -- now I get the rotating in-progress indicator, but nothing further. But, after about five minutes, I'm told Windows cannot access the setup file -- I may not have the appropriate permissions! Downloaded HD Tune -- same problem.
10. I'm unable to access the Registry Editor (not that I have anything in mind to do there -- just thought I'd try. Ditto Local Services.
11. I have run chkdsk and sfc -- all report clean.
I'm about ready to reset back to out-of-box state, create an on-line account right from the start, and see what that does.

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Coming back around from the dark side of the moon: performed full "back to out-of-box state" recovery; created on-line account using pre-existing outlook.com credentials, and now appear to have functioning built-in apps -- verified store, feedback hub, and movies & TV so far. Will now start configuring to personal tastes (e.g., restoring Quick Launch toolbar) and installing apps and files, constantly checking to ensure nothing changes things. I won't forget all the help you've given me -- THANK YOU!

Thanks again!