I have AppRadio DA100 with 8.05 from peoneerelectronics.com. (i have only 3 languages - Eng, Franse, Spanish or Italian)

But im from Russia and i need to install firmware for Europe from peoneer-rus.ru

When i've been connecting USB Flash to update my Europe 8.05 firmware, i got error - error with reading file from USB (something like this one)

How to DownGrade DA100 to my native Firmware??

As far as I know you can't downgrade to a version number of the same or lesser.