Bootcamp partition with Windows 7 no longer recognisable

It's the tool called gdisk, correct? So, basically, the steps I need to take are the following:

Rebuild GPT4 using start/end offsets

1. Sudo gdisk /dev/rdisk0
2. P (print the full list of parts)
3. D (delete)
4. 4 (part 4)
5. N (new part)
6. 4 (part 4)
7. 101003264 ( - Start offset in sectors or the start point for Bootcamp part)
8. +875767808 ( - Size offset, as opposed to End offset)
9. 0700 (Windows part type)
10. P (print list of all parts just to see what changes will be made)
11. W (Write the new GPT)
12. Y (Yes! really write the new GPT)

Rebuild MBR to match the new GPT information thus resetting the Hybrid MBR. Use defaults for other questions (like partition codes). The only values that need modifications are the Boot flags and step 10. Accept all other defaults that Gdisk offers. Please see thesample Q&A as an example. These steps can be repeated if you make a mistake before you get to Step 12, otherwise start from Step 1 for these steps. Step 6 has numbers which are typed with a space between the numbers. Please see the sample Q&A before you execute these steps.

1. Sudo gdisk /dev/rdisk0
2. P (Print list of parts)
3. R (Recover)
4. O (print current Hybrid MBR)
5. H (chooses Hybrid)
6. Partitions numbers to be hybridized: 2 3 4
7. Y (Good for GRUB question)
8. N (part 2 boot flag)
9. N (part 3 boot flag)
10. Y (part 4 boot flag make NTFS bootable partition)
11. O (print current Hybrid MBR)
12. W (Write the new MBR)
13. Y (Yes! write the new MBR)
14. Reboot

Let me confirm these steps with you before I attempt to do anything here.

Yes I figured out the macOS/BC Assistant was the one causing trouble this time, and not the hard drive. I had to downgrade my macOS to Sierra and do pretty much everything Boot Camp Assistant related from there, but hey it finally worked. I managed to make a new partition and install Windows 7 in it. If anything unusual happens again I will make sure to report here, but so far everything is good.

I can't seem to edit my last post anymore. But let me share the diskutil list and /dev/disk0 commands after the GPT and MBR rebuild attempt. It might help us somehow.

And also the hex dump of /rdisk0s3

I am still on High Sierra.

• diskutil list

• diskutil repairDisk disk0

EDIT: A small detail I forgot to mention. If I use Disk Utility to create a new partition, it works. It's the one I named 'bootcamp' in the first image. But I'm not sure if it's correct to create one through Disk Utility and not the Boot Camp Assistant.

No, I cannot see or find any files from my Windows partition. I searched for files right now on macOS High Sierra, but I'm pretty sure I did the same on macOS Catalina when this problem occurred. I also wasn't aware about Catalina being compatible with older Boot Camp installations, but after all that happened it's too late now.

After the 'w (write)' instruction I get the following message:

Device could not be accessed exclusively.

A reboot will be needed for changes to take effect. OK? [n] 

Is this supposed to happen? Should I let it reboot or is it an error? If it's the former than what should I type?

Also I believe I have SIP already disabled here.

EDIT: I ran 'csrutil status' and it says:

System Integrity Protection status: disabled.

Ok, I searched for similar cases where such instructions were given and apparently I needed to confirm the reboot to finish the whole process. I typed 'y' and reboot my Mac as instructed.

During boot I held the option/alt button and the Windows 7 partition reappeared in the disk selection screen. However if I select it it gives me an error, 'Missing Operating System.' The screen just stays there and I can't do anything but force shutdown my Mac.

Going back to Mac I still can't see my Windows partition or its files. It remains unchanged from the images from my second post (greyed out, inaccessible, impossible to mount.)