If you're passing your phone on to someone else or your phone has a persistent problem that cannot be solved, you can perform a factory reset
Factory reset is not a step to be taken lightly. It'll permanently delete all your data and customized settings, and will remove any apps you have downloaded and installed.
Be sure to back up any data and files you want to keep before you do a factory reset.
All you need to do is
1.Turn Your Phone In Off Mode.
2.Press and hold Volume up & Volume Down Keys then Press and hold Power key.
3.Do not release any key until you see Recovery mood Factory Reset options.
4.When you see options Release all keys
5.Press Volume up key to select option Recovery Mode.
6.Scrol down by volume down key to select wipe data and touch menu
8.Select yes delete all user data and touch menu again.
9.Wait and Select Reboot Device Option,
10.Your phone will be reset and in case if you forget password the unlock password and patterns will be removed.
