A2 is not an error - is the normal code when the OS is taking over the control...
When you're reseating the CPU, you will inspect it's socket for bent pins... you can take high res images of the socket from multiple angles and post them here... also inspect the bottom of the CPU, all those pads should look like the same - the point is to have all those pins aligned and in the same height...
When mounting the cooler, make sure that you have cleaned the previous TIM from both CPU and cooler (you can use isopropyl alcohol for it), apply fresh TIM (one blobb in the middle of the CPU) and tighten the cooler's screws equally in all for corners in an X manner...