Before you try the factory reset or hard reset on your device, make sure that you have backup your important files. Restoring the default settings or factory reset your device will delete all your existing files and will go back to its initial state.
Step 1. On your iPhone, go to "Settings".
Step 2. Select "General" option.
Step 3. On the bottom of the screen, tap "Reset".
Step 4. You will be seeing a list of things which you can reset. If you want to reset all the content, select "Erase All Content and Settings".
Step 5. Tap "Yes" to confirm the action.
Now, you just need to wait while your iPhone 6 is wiping all data on your device. In a short while your device will be good as new.
In case your iPhone 6 is unresponsive or frozen, you may need to hard reset your device. Simply press and hold the "Power Button" and the "Home Key Button" at the same time for at least ten seconds until the Apple logo appears.
Erase your device with recovery mode
If your device is not sync with iTunes or set up Find My iPhone in iCloud. You will need to use recovery mode to restore your device. This will erase the device and its passcode.
>>> Connect your iOS device to your computer and open iTunes. While your device is connected, force restart it:
>>> Press and hold the Sleep / Wake and Home buttons at the same time. Wait until you see the recovery mode screen.
>>> When you see the recovery mode screen. Choose the option Restore. iTunes will download software for your device.
Your device will exit recovery mode if it takes more than 15 minutes. You will just need to repeat the process to finish.
The instruction provided is the general steps on how to Hard Reset and Factory Reset.If the instruction will not work, please make a comment and we will immediately find the correct procedure. Thanks.