It shows “unable to verify update” , “failed verification because you are no longer connect to the internet” . Then I tried 2-3 times and change the networks also but it shows same !

Reset your Network Settings. Tap Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.

This wont delete your data. However always make a backup.

you can also try a hard reset:

Press and hold both the volume down button and the Sleep/Wake button at the same time. When the Apple logo appears, release both buttons.