i am Lesley , i work in a cellphone and communication company. we sell lcd screen, back housing battery for iPhone Samsung LG Sony and so on. we also repair cellphone.
Answer to "I phone not working"is your iPhone can work well before you update?
Answer to "iPhone 4 is working but screen is black?"take down the screen to see whethere the cable is broken or get loose. if not . maybe the screen is broken.
Answer to "iPhone 4 won't turn on all black screen"replace the lcd screen maybe is a good idea .
Answer to "iPhone won't turn on after screen replacement?"http://www.aliexpress.com/store/product/...-PCS-for-iPhone-5S-4-inch-IPS-OEM-LCD-Display-Digitizer-Touch-Screen-Frame-with/1294129_32222622185.html
Answer to "iPhone Not Fully Loading to Home Screen"connect the Phone with computer. press and homebutton and power key. when Apple LOGO show up, immediately release the power button and continue holding the HOME button until the phone shows a data cable link iTunes icon. then open iTunes icon on your computer, it will show links to be restored on an iPhone, click recovery point or restore the system you want to update. http://www.aliexpress.com/store/product/...-PCS-Black-White-100-Tested-High-Quality-LCD-Display-Digitizer-Touch-Screen-with-Tools-LCD/1294129_32219396130.html