I'm only aware of the phoenixsuit that can boot the box from a pc via usb by cable.
Or if you have a kernel in EMMC or SPI that can boot anything else from usb or wherever.
Usually if Allwinner SOCs are presented with an SD that will always take priority to boot. Can you see a fat formatted SD from Android?
First of all, Thank you for your answer Lumpi!
Unfortunately I can't see any formatted SD from Android, at this point I think that I have a HW problem with SD reader present on the box