Danieleczek, the filename can be anything you like. The way to flash it is by booting into dos and flashing it using command line tools.
1 - get a spare USB stick
2 - in windows download yumi https://www.pendrivelinux.com/downloads/YUMI/YUMI-22.214.171.124.exe
3 - run the exe, choose your usb stick (don't get it wrong), and opt to format it, and install balder (which is freedos).
4 - The flash drive will be labelled MULTIBOOT.
5 - download prr.exe and fpt.exe (attached to this message) and copy them to the root of your MULTIBOOT drive
get em here:
6 - copy the rom I posted to the same place, and rename it to v810mod.bin
7 - restart your machine and elect to boot off your usb stick in NON-UEFI mode (ie you need legacy mode) - you might need to change your bios settings to do this, or try pressing F12 as your machine comes back up and choose your USB stick.
8 - select balder and press enter - you should see an A: prompt
9 - type c: (and press enter)
10 type dir
11 you should now see the files on your USB's MULTIBOOT drive
12 type prr (enter)
13 type fpt -f v810mod.bin -bios (enter)
14 you should see your bios roms chips being written to and verified
15 reboot and press F2 to see your new unlocked bios (NB ethernet is disabled by default, so you will need to reenable)