I just tested mine. CPU is required (I used 5650G) and I had one stick of RAM in slot A1.
The IP of Managment I got out of my fritzbox (you neet to connect the managment port with your network first).
Connecting to the IP required the password (on the box or the mainboard itself). The System was powered on for the follwing process.
Under Maintenance>Firmware Update I uploaded the image.RBU of from the Gigibyte Update files. After that I selected “BIOS Update” and the flash was successfull.
BUT it did not show immediate success (“System Inventory” still was wrong), firstly I powered the system off via “Power Control” and gave it some time. After that i powered it on again via “Power Control” and the “System Inventory” did no longer show the dummy entries, but my correct CPU and Ram.
The BMC I did not try to update yet.