If your phone is fully functional (you haven’t messed up something while playing with custom ROMs, for instance), all it takes is:
Factory reset for your smartphone via fastboot
Factory reset via fastboot
1. Go into Settings -> ‘Backup & Reset’
2. Select ‘Factory data reset’
3. Then tap on ‘Reset phone’
4. Finally, touch ‘Erase everything’ and wait a few minutes until it’s all done. That’s it!
This is the exact steps you should follow on just about any Android smartphone or tablet – you can factory reset the Samsung Galaxy S5 this way, Note 3, the HTC One (M8), the LG G3, Sony Xperia Z2, Moto X, Moto G, and many others.
In case your smartphone is not starting up properly due to major changes or apss installation or corrupt latest downloaded software, you’d need some other tactics. Do the following:
1. Power your gadget off.
2. Hold down the Volume Down key and the Power/Lock key simultaneously for a few seconds. (This way you ‘fastboot’ your Android device)
3. After letting go, you’d see a menu with several options. Navigate using ONLY the volume down key. Go to ‘Factory’ and select it by pressing the volume up key. Your phone will do the rest of the magic, and will restore itself to factory settings in just a few minutes.