@Lost_N_BIOS

Thank you for wonderful support so far.

But I got a better solution. I have just received from the seller a copy of the original bios. See: https://tinyurl.com/y55ecbt5.
For this downloaded file, there are two bin files and an EFI folder. The file for the BIOS starts with EG. I am not sure what is the other bin file used for.

Must I copy the EFI folder into my C: drive?

I have somehow managed to restore my original BIOS successfully. The notebook is booting properly.

But the problem of my M2 SSD not being detected still remains.

I was wondering if my issue is related to the following post #1015 asking for a AHCI driver as it quite similar to the hardware id of my SATA AHCI controller(see post #1) :
Modded Intel AHCI and RAID Drivers (digitally signed) (68)

Hope to hear from you soon. Thanks.

@N.D. You're welcome! What did you mean for me to inspect that BIOS for, or what did you want to use it for? I sent you mod BIOS, this needs flashed in as I originally directed you to do, to try and get around the issue.
To see if changing SCC UFS Support to enabled helps or not, I see some reports of changing eMMC max speed to 200/250 helps too (Default 400), but that may be for other issues, unsure if those reports were about disk not showing up at all or just some other incompatibility.
But, we can test that change too once you show yourself proper method to reflash BIOS region. Some other stock BIOS isn't going to be any different than the stock BIOS you already sent me dumped via AFU from your board (It would need mod too)
Unless you meant to recover system, in that case, yes, it can be used, same as your original dumped BIOS region

I checked the BIOS package, this file is EC FW GLK_EC_G140J_V130806.bin and this one is BIOS E.G140J.S4.E1.002.bin

You can use this to reflash BIOS region too if you want, instead of FPT, but then you may run into AFU checking the BIOS and it not wanting to flash mod BIOS (with the mod one I sent you, but you can try), this is why FPT has been suggested from the get-go
AfuEfix64.efi E.G140J.S4.E1.002.bin /b /p /n
or just AfuEfix64.efi E.G140J.S4.E1.002.bin /p

Or you can use that FPT included there too, same as the EFI one you already used, but you need to use the proper command as I mentioned and not include location at the filename position >> FPT.efi -bios -f filename (no fsx:\ in front of file name)

EFI Folder is for booting EFI on USB, like you already did previously to Shell and FPT

Now, try again, the BIOS I sent you, properly flash via bootable DOS USB Stick as mentioned in my previous post, or properly flash via shell with FPT as mentioned here and in my previous post. Only after we test that edited BIOS, can we next test the eMMC speed change, other than that I don't see why it's not working.

I have no clue what you mean with your last thoughts about AHCI driver, seems unrelated to me, drivers would only be loaded/required, once the device is detected in device manager (until then it's dead to the system, not there, so no driver can be used)