Well, maybe I should wait for 20H1 and afterwards do a clean install on this PC and an inplace upgrade on the other two.
If You want disable system restore permanently go to task manager go to services tab,on botom select open services when open select standard search for Microsoft Software Shadow Copy Provider select it , right click open properites stop the service and select startup type to disable do the same with Volume Shadow Copy
So, I did an inplace upgrade and although it fixed the desktop icons and the firewall it oddly had some updates to install when I downloaded the latest build and disabled Edge's extensions. Anyway, I successfully installed the updates but I noticed virus & threat protection is broken, even before installing the updates. When I click on it (virus & threat protection) it's blank and it states it is managed by my organization, whatever that means. It looks like I should have done a clean install but I can't do it on the other 2 PCs (and they may break like mine after doing another inplace upgrade) but even so I'd still have to install (I guess) updates when I downloaded the latest build but that would be the less important as long as it was ok. Let's see if it won't screw future updates too (on this PC, at least). I don't know what is causing this "Some settings are managed by your organization." message to appear and prevent me from changing some settings in which it appear. EDIT: It looks like NTLite and/or Winaero Tweaker are causing this message to appear (as well as some policies I manually set on gpedit.msc) because they add some policies on gpedit.msc (and maybe they make another modifications) but I don't know why I can't change the settings without reverting the policies (I want to have them but still be able to change the settings because not only I may change my mind regarding them but also because they prevent me from making another changes on settings which aren't directly related to these ones) which I don't even know where they are. On NTLite it's possible to set the policies and let the users change the settings afterwards or not without reverting the policies and maybe the other mentioned programs only set the policies and don't let the users change the settings without reverting the policies. After reverting the policies the mentioned message disappears and I can change the settings.
I have no clue why even the most proven fixes, like an inplace upgrade, are not working for you. When an inplace upgrade is done, using an uptodate ISO, the build should be at that level, when you've used an UUP dump generated ISO, it probably is at the level of the created ISO.
I didn't do a thing and I was still offered the updates. Anyway, virus & threat protection is no longer blank and stating it's managed by my organization so the problem is fixed. So, in the other 2 PCs' case, should I use this ISO to do an in-place upgrade or should I integrate the latest updates on a 18382.1 image with NTLite and do an in-place upgrade? Maybe it won't screw up Windows and detect new updates, not to mention it won't be so slow to create the image. How can I remove Adobe Flash Player and the Malicious Software Removal Tool? Msconfig's name is still in english and not in my native language, I still can't disable some security and maintenance settings (the windows update, microsoft account, spyware and unwanted software protection, windows activation, device software, startup apps and homegroup [I thought Windows 10 had removed homegroup] ones since it won't let me click on them), still nothing happens when I copy certain folders to the windows sandbox and I still have non-empty folders with an empty icon. Let's see if empty folders on the Documents one keep on being automatically deleted. Internet Download Manager became broken so I had to reinstall it to fix it and now my USB devices appears as "unspecified" on the control panel. EDIT: I forgot to say that even after doing clean installs (even when using untouched images) I still can't disable some security and maintenance settings (the ones I mentioned earlier), msconfig's name is not in my native language and nothing happens when I copy certain folders to the windows sandbox. Also, which focus assist's setting should I use since I don't want to have notifications and may I still have them if I don't touch focus assist (the same with leaving it with the priority only setting checked and not messing with the automatic rules' settings) after disabling notifications on "get notifications from apps and other senders" as well as the 5 below settings and on "get notification from these senders" below? And may I still have notifications if I don't touch focus assist (again, the same with leaving it with the priority only setting checked and not messing with the automatic rules' settings) and disable "get notifications from apps and other senders" as well as the 5 below settings and on "get notification from these senders"?