Modified for what? Original product bios file website? Original current dump/backup of the system bios… this are things that it may be handy in order to users help you, agree?
The bios is Legacy or UEFI, it cannot be re-coded.
EDIT: If its a based ECS H61H2-CM, both bios 4.6.4 and later one 4.6.5 are UEFI, the later on adds CSM sub-menu.
For NVMe mod on both models, follow the guide: [HowTo] Get full NVMe Support for all Systems with an AMI UEFI BIOS - Special Topics / NVMe Support for old Systems - Win-Raid Forum (level1techs.com)