Good that you fixed serial…
Ra0/rax0 are names from closed source driver…in mainline openwrt there are different interface names,also wifi devices are bridged afair,so you see maybe only 1 interface.
You cannot flash emmc from sd as both share same controller and only 1 can be used at one time…you have to flash emmc from nand or nor. And you cannot flash same image from sd to nand/nor…memory layout and boot binaries are different (last also for emmc).