In order to hard reset a Philips F515, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Philips F515 device will be brought back to the default configuration of a brand new device.
1. Press-hold the Power button until the phone powers up.
2. Now open the dialer and tap in the code: #20021208# or *01763*737381#.
3. Confirm the factory reset process and wait for your phone to reset'n'restart. That is all.