For Samsung, simply open your Samsung’s phone app. Enter *#0*# using the dial pad, and the phone will immediately go into its secret diagnostic mode. Note that the process is automatic, so there’s no need to tap on the green call button to enter the command. So if you enter the code and nothing happens, the feature is disabled on your device.
For Iphones, the process can be conducted simply via installing free apps on Apple Appstore. To name some apps, they are Sensor Kinetics, Test and Check for Iphone. Also if a person checking these functions is a professional technician or a regular Apple product user, he or she won’t find it difficult to detect if the screen is an original one or a duplicate one. There are other small observations that can be made to check if the display is original or not by looking at the fonts and icons and color sharpness.