I am using the latest version: 3402 on an X570 mainboard. Originally, version 1005 was installed. The BIOS update (.cap file) can be found at ASUS.COM and installed with BIOS tool AZ-Flash. It can take quite a long time (> 10 minutes) and you also have to be patient during the first restart: PC looks almost "dead" for several minutes! At the end everything is OK again.
Good luck and success!

No, I have the 3900x. But it shouldn't make any difference.
Take a look at the video from the 8auer about this board.
There is a k iff with the graka at the first start.

I can no longer say exactly. In any case, it's not the most recent one. I updated it first. It went without a hitch. (>20MB)