In order to hard reset a Cube i6 Air, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Cube i6 Air device will be brought back to the default configuration of a brand new device.
1. Power up the phone.
2. Press-hold Shift. As you hold it, tap Restart.
3. In the next step choose Troubleshoot.
4. Now select Reset your PC and Next.
5. Now choose between Just remove my files and Fully clean the drive.
6. Lastly, select Reset. Done.