[Q] Is D618 need 2 aboot.img to unlock booatloader? topic

I tried to port rom to D618 but after flash the ROM it is bootloop on "security error".
I have unlock the aboot.img and flash custom recovery but why it is locked after flash the ROM?
Is D618 need 2 files aboot.img to patch? I mean aboot.img and abootb.img?
I have pull abootb.img from D618 but I'm too afraid to have hard brick when push the patch one.
If I mess the aboot.img, can I still get into downlaod mode?