Flashing the compiled AOSP into Hikey970


I compiled the AOSP for hikey970 and want to flash it into the board.

1- “fastboot flashall -w” fails with the error: requirements not met! in checking product stage (message: device product is 'Linaro", update requires ‘hikey970’)

2- When I manually flash just system.img into the board, the board will boot and is OK, but when I flash system.img, userdata.img and cache.img then the board will not boot. So if I want to flash files manually, which files, should I flash?

3- If I want to have a little modification in the source code, then I should recompile all of the AOSP? And also which files are affected and I should flash to the board to see the modification?

I would appreciate if anybody can help.