Depends on the BIOS version it's shipped with but even if it's a older BIOS version the CPU-less feature to update it seems easy enough.
View: https://www.youtube.com/watch?v=iTkXunUAriE
Yes.The B450 Max motherboards are shipped with bios that works with Ryzen 3000 series but will it be backward compatible with older CPUs like 1600 AF or 2600 or not?