What you currently have is a nice paperweight since when BIOS update is unsuccessful, it will brick the MoBo.
You can reset CMOS as much as you want but it doesn't revert the BIOS version back to the one it was. What CMOS reset does, is that it reverts all user made changes within BIOS back to the ones they were once the BIOS was 1st installed (e.g factory default).
Sadly, there's no way you can revert back to the older BIOS. And at current point, you're looking towards new MoBo.
Only way you can "fix" your MoBo is when you physically replace the BIOS chip on the MoBo with another BIOS chip that contains older version of BIOS. But that needs soldering and you have to have compatible BIOS chip, unique to your MoBo.