This is how to remove unlock pattern, remove password on your Lenovo K920 Vibe Z2 Pro Android phone wipe all data
Power off your Lenovo K920 Vibe Z2 Pro phone.
Press and hold Volume DOWN and press POWER button to turn on the phone.
When you see the LENOVO LOGO release POWER but keep pressing the volume key until a menu with a numbered list comes up.
Use the volume down key to select "6. Factory reset" in the list and press power. Note! This will delete everything, all of your data including SDcard files. Be sure to backup all of your data before doing a factory reset!
Wait until the phone reboots. The first boot will lasts a little longer than usual. Be patient.
Lenovo K920 Factory reset the soft way from the menu if you are able to access the phone:
From the Home screen, press the Menu Key and touch Settings.
Touch the Backup and RESET
Touch Factory data reset.
Touch Reset phone.
Touch Erase everything.
General advice: Before you buy a new cell phone or new tablet, please try the following procedure to repair your device in a software way. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card before doing factory reset. It is impossible to recover your data after doing a hard reset, so online backup is always important. For all of your data, a backup should be done on an external device, hard drive, raid system or media. With or without insurance, if your cell phone lost, damaged or stolen at least your invaluable data is backed up in a safe place. If you are about to sell your phone and you want to wipe your personal data, or if your phone affected with virus you have to do a hard reset. In some cases, you can delete the forgotten password or lock pattern from your device as well. All information is for devices with stock based ROMs. If you are using rooted device, always back up your EFS folder first, containing your IMEI info, etc.! Please also note, that a hard reset operation will not unlock your mobile phone's SIM lock or network lock, but it will remove the unlock pattern, remove the user password or PIN password (NOT the SIM card's 4 digit PIN code). Also note that the firmware version will not be affected in any way, it will not be downgraded, it will remain the same you are using and if you have rooted your device, root privileges remain also unaffected.