Wow, lots of questions there. I have had many years of experience as well and this Dual boot design is not very good. From what I have found so far, you set the BFB2 bit to force the internal ST bootloader to use Bank2, but there has to be a valid ve...

I have had similar issues using the STM32L4R5 on our custom board and working with the support team to get answers. Apparently there is some issue where this "PEMPTY" bit in the status register can become set while trying to switch banks and it can c...