What really causes error code 9, AND an endless power-on loop?

It’s been a while since I posted a question. Here is the latest on my iPhone SE (2016 version).

I actually did have a display, and for a short time, the touchscreen worked!! Oops…I guess it didn’t work.

On the passcode screen, the words “Emergency” and “Cancel” were underlined. I have no idea why. All I know is, I entered the passcode, and my phone said, “Press Home Button To Recover” (something like that)…but my home button wasn’t working, so my phone went back to this endless Apple logo going on and off . I have tried using iTunes to recover it. I got error code 9. I tried pressing the power & home buttons at the same time and then pressing the volume up button until it becomes obvious that nothing is going to change. I think the logic board just needs all new FPC connectors. Would that bring my phone back to life??

I thank you for your help!! Stay safe!!