Why is the folder under \Users that my account used the only one with permissions problem after connecting the HDD through a USB adapter?

Keeps saying "click continue to permanently get access to this folder" (which obviously doesn't work... assigning permissions in the security tab doesn't either, keeps saying it's not ready... I was able to access it using a USB live OS...)

As I said though, I try to change it from the security tab etc. and it fails, every option there seems to be fails... I just don't understand why it's just this one folder and not the many others too, though, or why I can access it from a linux live os but not w11...

And what that .reg does is that, despite seeing lots of successes apparently, after the cmd finishes the folder still asks the same question...

Nothing else?

I have run into this problem multiple times when dealing with data on old system drives where files were created by a different user account. Despite what is supposed to happen, 'take ownership' within windows does not always work when an old system drive is connected externally or as a second drive. Advanced permission settings WILL work if done exactly right, but it is quite tedious and most people do not know exactly how to do it.
It is much easier and faster to do what you did (use a live usb OS that doesn't care about permissions) to access the data rather than deal with permissions within windows. I always use that method in such cases.

Something else of note, people do not realize when dealing with such data that moving data from one drive to another retains original ownership. Within Windows, files must be copied and pasted by the original user account from a system drive to external media on the machine where the files were created . Ownership rights are not retained in that case. Anyone can access the files from the external media.

Issue with a live usb os is that it's extremely slow to even access the data (besides copying)... took half an hour just to confirm how many gb there were... and with the limited folders I could access from a usb adaptor to w11 it seems to be normal speed (for the former I thought it was the hdd itself that caused the slowness, as the last time I could access the w10 installed on it the corruption resulted in extreme slowness despite files being local, but accessing the few from w11 makes me wonder... as of now I can't access w10 at all, keeps looping a need to diagnose and fix...)

So, it would be much more useful if I could access it from w11, and if this permissions thing isn't a result of hardware corruption then windows is being really annoying (as trying to change permissions from the security tab seems impossible due to corruption...)

I don't understand why it's my account's folder that is inaccessible... even system folders are, even other account folders, just not the one I need...

It is slower using a live usb. Since I access user drives multiple times a year, eventually I installed Linux Mint as a VM for no other purpose. As far as changing all the permissions, it depends on the file structure and size of the folders whether I attempt to deal with permissions. In case you are interested, here's a little tutorial I wrote for myself regarding changing permissions. I do it so infrequently it's easy to miss a step.

Yeah, changing permissions like that is what I tried but as mentioned the hardware corruption is seemingly not letting me finish changing them, does a few files but then stops, saying the disk isn't ready, wanting to fix it (but that fails too...)

Have to attempted to repair the corruption on the drive?
Open command prompt as administrator and type chkdsk x: /r (replace x with your drive letter)

Yeah, tried everything, it just goes into a loop, restarting and trying to repair again and again... just need to get the data off it as I assume it's a hopeless disk, individual files have already been corrupted randomly (and certainly not repaired after any attempt)...

Then IMO if the disk is corrupted that badly, using a Linux distro to recover what you can is your best bet. The times I've used a Linux Mint live usb it has been slower, but not so slow that I couldn't get the files. It sounds like the disk is in such bad shape even Linux is having a problem reading the data..

Well, it had trouble reading the specific files that I couldn't even move when I had access to w10 on the same drive too. HDDs are so weird, the only indication of this I had at all were these really long freezes I used to get, then suddenly it wanted to scan and fix (which failed) and I found that random files were corrupted... until now it doesn't even bother asking me to skip the scan on boot and keeps looping with it... fails DST too.