which BIOS version does this mainboard have

Yes, the Ryzen 7 5700X processor is compatible with the ASUS ROG STRIX B550-A GAMING motherboard. Both parts use the AM4 socket, and the motherboard supports the AMD B550 chipset, which can work with the Ryzen 7 5700X. However, it is advisable to ensure that the motherboard has the latest BIOS version to ensure smooth compatibility.