if you mean using the upgrade process and choose the old firmware i already tried that and got this error (RUNME:cannot downgrade!!!) system upgrade failed , is there a way to bypass that
Are you sure about the firmware if it's a signed firmware?
if it's unsigned firmware it won't work but if you flash it with sig firmware it should be work.
Anyway, if your miner has an SD card slot you can try to contact bitmain and ask for an SD card image. I'm sure their image is a lower version.
You can follow this guide from here
SD card flashing with customized PW