Doesn't boot, charge, not detected on pc/mac

Borche Gjeorgiev , I think you got your answer already:-) "Even with full battery phone doesn't boot." which it should, even with a bad lightning connector unless it shortens out the board, which is unlikely. I'd suggest that you remove the logic board and only attach the bare essentials like a known working lightning connector and a good display assembly as well as home and power button. Make sure that your power flex is okay. It should start with that. If it does not, you are pretty much guaranteed to have logic board issues. Possible damage from using the wrong screws, so check your board extremely careful. If it does start add the other components one at a time and see what works and what does not. Never assume anything and test every component. Supposing and assuming in a case like that will lead you down the wrong path.

It sounds like the logic board probably has a short somewhere. There are ways to find out where it might be but first it is probably best to look over the board under some sort of magnification and see whether you can notice any damaged or knocked off components.