Hard Reset Microsoft Lumia 535, 430, 435, 532, 540, 550, 640, 950, 1030 - Factory Reset
Hard Reset Micorsoft Lumia 532 - how to completely wipe your phone
How to Hard Reset MICROSOFT Lumia 950 - Remove Pattern and Password Lock
Hard Reset MICROSOFT Lumia 950 - How to Factory Reset in Windows
Hard Reset will erase all of your data
All described operations you are doing at your own risk.