Para po makapagflash ka ng stockrom with lower bootloader/binary version at android version, need po iunlock ang bootloader ng iyong device, kung hindi mo po maunlock, the only way to flash stockrom is either using the same binary/bootloader version of your device or flashing its latest stockrom...
Pakitry po muna ito, download OTA Update ng iyong device, ilagay sa memory card, go to recovery and select install from storage, tap from ext storage and select downloaded ota, tap ok, wait mo magupdate👍
Make sure na tama ang binary/bootloader version na gagamitin mo, base sa phone mo, U5/binary 5 yan, hanap ka ng firmware na same ng binary then flash mo sa odin👍