What happen to my iPhone 6+?

Hello there. Recently, I dropped my iPhone 6+ and I can't turn it on , so I replaced the old battery in to it and it finally came back.That is the first time I open up an iPhone, I unnecessarily detached the screen's cables and attached it again.

After that, my iPhone 6+ front camera and front speaker are not working anymore, I think I did crack that cables. But the sensor and Touch ID is still working.

For the rear camera, it's like magic, sometimes it came back for a while and die again, I didn't detach the rear camera at all... A way to turn on the rear camera is to detach the screen (keep connecting the cables) then boot it up again, the rear camera will works again; However, once I attach the screen, the rear camera will freeze and no longer working.

So, the situation is

Front camera : DEAD

Rear camera : DEAD

Front speaker : DEAD

Flash light : DEAD

Question : What happen to my phone? I think the front camera and front speaker can be fixed by replace it. But how about the camera and flash light? These things dead is the camera and flash light problems or the logic board ? Please help!