Lucas

what about replace a keypad?

i guess your battery is loosen

oh, i suppose you have the same problem as this guy dropped in water. Black screen except in sunlite. touch screen works try under sunlight, if you can see something, then the same as above one, if not then your LCD is totally damage. but whatever it is partly or totally damaged, all you need to do is replace a LCD. Hope this can help you. please vote if you like my answer, thank you!

the backlight of LCD is damaged while display function is ok...so you have to replace a LCD

i have no idea which part do you refer to since no pics provided. but as to your requirement, i did found an very very detailed video for you. Incredible Detailed iPhone 4 CDMA Assembly Video Hope this can help you find out your tiny parts. If this still cannot help you, then i have no idea...

back plate? do you mean the rear housing?

oh...try restart it see if still the same

cutter: cut the big card to fit the small tray adapter: adapt the small to fit the original big one... i guess that's the difference, if you want to get one for the iphone 5, i think you need the cutter.

got very hot below the front camera? perhaps the logic board got heated. check it

i afraid that it is difficult for you to attach them because they are usually assembled by machine. and why do you buy them separately? it can be expensive than buy an assembled one