A:For the Intel Z270 motherboards with two BIOS ROM chips, there is no need to switch BIOS ROM when doing recovery.
When booting properly, the system works on the active BIOS_A1 as picture below.

However, if the active BIOS_A1 is corrupted or damaged, after several failed boot attempts, it will automatically do BIOS recovery from the backup BIOS_B1 and then the system will still work on the active BIOS_A1. And the monitor will show Secure Backup UEFI (B-->A) function as picture below.

After finishing this function, the system will reboot and work on the active BIOS_A1.