How to hard reset nexus 7 tablet
ASUS Google Nexus 7 / 2012 - Password Removal, Backup & Factory Reset / Wipe Data
Hard Reset ASUS Nexus 7 - factory reset by TWRP recovery
Nexus 7 Hard Factory Reset Fastboot Bootloader Recovery Mode
Hard Reset will erase all of your data
All described operations you are doing at your own risk.