aspire E5-571G BIOS downgrade

Hi

i have problem with acer notebook e5-571g. notebook have discrete graphics nvidia 840m. i flash notebook with new bios version 1.31 (from bios version 1.26) but after flashing new bios (v1.31) no 3d application or games can not recognize my nvidia gpu only intel integrated gpu. i need to downgrade my bios to version 1.26. how can I do?

when download bios (v1.26) from acer support page
try flash bios with older version
error say version of rom file isnt newer then version of bios

Thanks in advance