Over-night charged iPhone 5 not turning on, no matter what

Hi,

I over-night charged my iPhone 5 five days ago, noticed in the morning the whole phone was scorching hot!

I immediately unplugged the charger connected and let it cool down naturally.

The screen was black and I tested out to see if it turns on, doesn't at all.

So I opened the cover and unplugged battery out of it to reset and inserted back in.

Still doesn't turn on. I swapped the battery to different one and nope ):

I could see the clear sign of mild burn inside and on the inner wall of cover (Brown color change spotted around inside).

Anyone know how to fix this? or which parts I most likely damaged???

I searched around Google and people hinted that usually motherboard get damaged by heat. Is replacing the motherboard easy? If it's not likely to get fixed then is there anyway to take out saved photo and datas from iPhone that's not turning on???

HELP ME SAVE MY BEAUTIFUL PHONE PLEASE ))));