Holding the power button down 60 seconds turns the device off even if frozen. I got stuck at a flickering blank screen while watching FB videos. I have no idea why it did what it did, battery shouldn't have been dead either but now it's charging, giving me a charging symbol, but won't turn on.

WARNING!

You have to remove the sim card tray before removing the daughterboard. At nno point in this guide is this mentioned. You risk damaging the daughterboard when trying to pry it loose.