How to force Onkyo to update firmware to older or current version

Today I decided to finally root my current Onkyo firmware, but the system wouldn't update, as it considered this update is not a newer version.

After looking through file headers and disassembly of, I realised that it relies on filenames in header`s file tree to determine firmware version.

I thought this to be a pain in the ass to rewrite and re-calc CRC for every file and googled to see whether there is a way to force usb update. (At first I thought factory reset might be able to help). Fortunately, yes, it's possible just to force it via USB. (Strangely, I remember flashing same firmware numerous times without any issues when I was first experimenting with reversing Onkyo encryption a year ago).

Anyway, firmware files must be extracted to the root of USB drive.

Disconnect Ethernet/Wifi, just in case.

Insert USB drive. Hold 'USB' button and press 'ON/Standby'.

Message "[Enter] USB update" shall appear. Hit 'Enter' to start flashing.. wait and pray there is no electricity cut-off =)