1. By typing "*#*#4636#*#*" you will be redirected to phone information menu. This code allows you to check information about your phone, battery, battery stats and WiFi. 

1.1  Phone Information - Here you can check your IMEI number, Signal strenght, cellinfo and connection type. Also you can run Ping test too.

1.2  Battery Information - This page shows your battery properties like: battery voltage, temperature, battery technology and device running time.

1.3  Usage statistics - This one displays your last app usage period.

1.4  WiFi Information:

- Wi-Fi API - Here you can disable current WiFi network, disconnect connection, get information about connection and other stuff.

- WiFi Configuration - On this page you can check information about connected network

- WiFi Status - Read about connected network and run Ping test



2. Typing this secret code "*#06#" you can easily check your IMEI number.


3. Calendar *#*#225#*#* - check your events in calendar

 

4. Debug info for Google Play Service  *#*#426#*#*

 

5. Access Google Partner Setup *#*#759#*#*