The format you have there looks to be just raw hex values.
I have converted it to a binary file, just to see what it looks like but it looks random to me.
Usually with raw firmware you see repeating patterns and often text towards at the end of the file where data is kept, but i see none of that
So I'm 99% sure that file is encrypted.
That's what everyone does when releasing firmware for a commercial product to stop anyone (china) copying it. The bootloader would have the decrypt key and decrypt that file before writing to flash.
So you would need an un-encrypted copy to write it yourself directly since you don't have the key.
Here's the binary version.
To program it you set AVRdude to raw mode, that's... -U flash:w:file.hex:r
but i'm sure it's encrypted so it's not going to work.