Few settings are still stored in CMOS, most settings are stored in NVRAM- Removing the batteries will clear CMOS, but most often not NVRAM, but some (very few) manufacturers have a routine for resetting NVRAM in case of non- booting device.
Nothing of this would help you since you possibly changed bios code. A bios recovery procedure could help if implemented.
Manufactureres bios: Be careful, that’s still only a bios region, you’re missing relevant parts as mentioned. This is not a complatet firmware!