"Why is the volume button stuck on my ipad"に関する回答I think you need to replace the volume button module.
"iPod won't power on after screen replacement, even when plugged in"に関する回答Make sure that all cables are plugged in, and that no cables are damaged. If you used a heat gun, it may be possible that you accidentally fried a cable while melting the adhisive.
"Is my circuit board fried or can I fix it?"に関する回答The Logic Board is fried. You need to replace it.
"screen shows thick vertical white line"に関する回答I believe you may have either left a cable disconnected, or you damaged the LCD. Check inside for any disconnected cables, and it there aren't any, order the iPhone 4 LCD replacement.