The phenomenon of hidden cameras in hotels or private places. These are some tips that you can check

Before Android 5.0 (Lollipop), doing a factory reset on your Android phone would restore it to its original state like it was brand new. From Lollipop, doing a factory reset in recovery (when the device is still associated with a Google account) still requires that you supply the credentials of the Google account associated with the device before the factory reset was done. This is called Factory Reset Protection (FRP), a security / anti-theft feature. 
If you find yourself locked out of your phone after a factory reset then this guide will come in handy. 

How to remove / bypass Factory Reset Protection (FRP) on an MTK phone

#505962; font-family: "Exo 2", sans-serif; font-size: 13px; font-weight: bold;">Method 1: Setup selection

During setup (using the setup wizard), do not connect to a Wi-Fi network. Also, untick "Protect this device" 

Method 2: Using SP Flash tool

* Download the firmware for your phone model @ https://forum.hovatek.com/forum-89.html
* Using the SP Flash tool guide @ https://forum.hovatek.com/thread-159.html, flash by selecting the Firmware Upgrade option

Method 3: Miracle Box method

Follow the method @ https://forum.hovatek.com/thread-13335.html ; select Clear Anti-Theft

How do I avoid the stress of factory reset protection when I need to do a factory reset

Navigate to Settings > Accounts and delete / sign out of the Google account associated with the device