Keypad shortcut for accessing internal features of android smartphone

Samsung Android Phone (You can try for several other phone also; codes are similar for most phone)

*#06#
IMEI (MEID) and S/N

*#07#
SAR Level

*#0808#
USB settings

*#7353#
Test software function like vibration, melody, Bluetooth, camera, speaker etc.

*#1234#
Version

*#0011#
Service Mode

*#1111#
Service Mode

*#2222#
service Mode

*#0283#

Loopback Test

*#0*#
General Phone Test Mode

MI Phone(You can try for several other phone also; codes are similar for most phone)

*#*#4636#*#*  

Phone and WiFi Information

*#*#64663#*#*
Hardware Test

*#*#1111#*#*  

Charge and Battery Status

*#*#2222#*#*  

SN

*#06# 

Mobile equipment identification (IMEI)

*#*#225#*#*
Calendar Info

*#*#426#*#*
FCM Diagnostics

              

Nokia Phone(You can try for several other phone also; codes are similar for most phone)

*#06#   

Mobile equipment identification (IMEI)

*#07#
SAR Level

*#*#4636#*#*  

Phone and WiFi Information

*#*#372733#*#*
Service Mode

iPhone(You can try for several other phone also; codes are similar for most phone)

*#06# 
IMEI

*3001#12345#*
Field mode

*#67#
Bill balance

*777#
Account balance

*#33#
Configuration

*#76#
Operator  

*#21#
Call forwarding

*3282#
Information

*3370#
EFR mode