As a general rule, a BIOS flash *may* be necessary ~once per windows upgrate - - at the most.
DO NOT use this as an fixall solution, as getting it wrong can brick your system.
It's the computer equivalent of russian roulette. The only exception I know of is if an update is required to fix a specific hardware issue and recommended for that purpose by the manufacturer.
The motherboard is over six years old so I'd be wary of doing more than upgrading your graphics card. It's going to be hard to find the answer to your question. You could try MSI support but myself I'd play safe and forget the CPU upgrade.
