Ensure your PC is connected directly to the ZTE router via Ethernet (Wi-Fi works, but wired is safer).
: Quickly download a "Button Mapper" app from the Play Store. Use it to reassign a remote button (like the "Back" or "Home" key) to open the System Settings menu instead of the default locked home screen. Method 2: Enabling Sideloading (Third-Party Apps)
You must know your exact hardware revision (v2.0, v2.5, etc.). Wrong firmware bricks the device.
telnet 192.168.1.1
To prevent the ISP from locking you again, kill the remote management daemon: