We are folowing the bios recovery procedure. the zip file you linked does not contain a .ROM file, the BIOS file in there appears to be xxxxx.504. Should we keep the file extension as is and rename that to SUPER.504 or adhere to the steps and change the extension as well to get SUPER.ROM?
No, you need to rename youre xxxxx.504 file to SUPER.ROM. When you invoke the recovery part in the bios, it will search for SUPER.ROM in the root of your usb stick.