Identifying whether display is broken or the motherboard I assume it is possible to damage the motherboard / chips inside a phone if it falls on the ground. So my questions is, is it possible to confirm what has been damaged during the fall?

I don't want to end up buying a replacement display and then found out the problem is somewhere else.

The phone is JiaYu G3T (a Chinese brand), fell on a ground. I completely disassembled the the phone but I didn't find any damage anywhere, everything looks like new. 

Pic 1. This should be black with a green logo, left part of the screen is darker than right



Pic 2. Again, half of the screen is darker, color problems at the bottom OR sometimes the same as the startup screen - grayscale-kind-of-inverted-colors display
You can use ADB to test phone functionality. ADB tool can be obtained from Android SDK. There are a number of test commands which you can use to test your phone. Steps are as follows:


cd to your ADB directory.
Connect your phone to PC via USB.
type the following command:

'adb devices' (without quotes)


You should see your android listed in the CLI. You can also enter device shell:

'adb shell' (without quotes)


List SD card contents:

'ls -l' (regular unix file navigation commands)


If you can access your device shell, it's most likely that your motherboard is working fine. There are several commands to check as well:

Sending user touch events to Android:
adb shell input keyevent &lt;event_code&gt;
1 --&gt;  "KEYCODE_MENU" 
2 --&gt;  "KEYCODE_SOFT_RIGHT" 
3 --&gt;  "KEYCODE_HOME" 
4 --&gt;  "KEYCODE_BACK" 
5 --&gt;  "KEYCODE_CALL" 
6 --&gt;  "KEYCODE_ENDCALL" 
7 --&gt;  "KEYCODE_0" 
8 --&gt;  "KEYCODE_1" 
9 --&gt;  "KEYCODE_2" 
10 --&gt;  "KEYCODE_3" 
11 --&gt;  "KEYCODE_4" ..... etc