Today I received a reply from Gigabyte (Gigabyte G1. Sniper A88X).
I am very pleased with the speed and honesty of the response.
Gigabyte has no information about the BIOS revision on the basis of the serial number.
Because of the product warranty (guarantee) I need to go to a service where I purchase a motherboard.
I purchase ~930 USD computer parts in that store, and now I have to pay 20 USD extra for a BIOS upgrade.
The problem is that there is no service in my town and I have to travel cca 60 miles to another town (capital city).
The good news is that I need on Saturday to the airport, so I'll carry the motherboard with me.