So I've bought an iPhone 3GS on eBay which has a few issues one of which is the battery (which I will replace), the other...

So i replaced the screen on my 4S (first repair on an iPhone i have done) and its gone okay, everything works just i...

so i am planning on replacing the front panel digitizer on my ipod touch 2g as the glass is cracked (the display itself is...

If the screen was already damaged then it can become pretty fragile. Your brother sitting on it probably cracked the LCD panel which is why it is covered in lines as you mentioned. The digitiser (part that recognises touch) is probably also damaged which is why you can't use the device properly . Have you tried a hard reset (holding down the power and home buttons until the device powers off and then continue to hold them until the apple logo appears)? Sounds like you'll have to replace the screen to be honest

have you tried to do a hard reset on the iPhone? (Hold down power and home button but don't swipe to power off and let go once the apple logo appears again) If that doesn't work then make sure the iPhone is running the latest IOS and restore it through iTunes (just make sure you backup your data first) Let us know how you get on :-)

Is it recognised by iTunes? might just be the screen that has been damaged as even tiny cracks to the lcd can render it useless? If the phone isn't recognised or showing any signs of life it could have caused tiny cracks on the logic board

Is there a darker spot above the area that won't work? Not much you can do as it sounds like the digitiser has been damaged so you'll have to buy a new display (can't just order the digitiser as it is fused to the led screen)

Try a hard reset (hold down power and home buttons until the phone shuts off then the apple logo should appear). If that doesn't work try restoring the iPhone (make sure you backup in iTunes before)

It sounds like something has shorted on the board. Did you disconnect and remove the battery? Not doing so means there is still power going through the board (even if the phone is powered off) Only other thing I can think of is a static discharge has damaged the screen connectors