A lot of time too entangled with our phone and ended up causing failure we do not know how to repair, will not start, only blocks me, we caught no network signal ... Well, with SmartFlash leave our phone factory-fresh.
The common problems are:
SmartFlash Tool completly erases device memory during flashing. Phone will make Factory Reset at first boot after flashing! You can upgrade and downgrade. This also will remove phone lock if you forget unlock code or pattern.
This method doesn't need internet connection.
Connect phone in S/W Update mode with battery in it (on the phone that is switched off, plug in USB cable WHILE HOLDING Vol+ button)
After successfully flashing, phone will reboot and make Factory Reset. And that's all!