Do I need to flash my SD card again with an image or can I just use my Raspberry Pi 3 MicroSD Card without any changes and plug it into my ODroid? I ask this because the image name "batocera-20171006.img" is the same for both architectures.
you need an other card.
the boot part for example is not the same one.
some other part of the system are different too, like the linux kernel.