Ok so I searched a lot for this answer and came up empty handed .. so I will try to be more specific :
let's say that I have a Samsung Galaxy S3 , I already know that my phone supports version 2.0 , but if I make an app or a game with version 1.x will it still run ?
On
From the android Developer Site:
Android supports several versions of the OpenGL ES API:
OpenGL ES 1.0 and 1.1 - This API specification is supported by Android 1.0 and higher. OpenGL ES 2.0 - This API specification is supported by Android 2.2 (API level 8) and higher. OpenGL ES 3.0 - This API specification is supported by Android 4.3 (API level 18) and higher.
Since all android devices support 1.0 and 1.1 you should be fine.
Link: http://developer.android.com/guide/topics/graphics/opengl.html
SHORT ANSWER:
Yes, your 1.x app will still work with OpenGL ES 2.0 Android devices.
DETAILS TO CONSIDER:
There is cycle of development for OpenGL that allows OpenGL ES 1.x to be maintained but who knows for how long. OpenGL ES 2.0 came out in 2007 and then last year OpenGL ES 3.0 released publicly. OpenGL ES 1.x is going to die soon.
This graph of usage might be of interest for you:
From this you should see that only 0.2% of Androids support version 1.1 only and everything else uses 2.0 & 1.1. I would start using 2.0 if you plan on long time support of you OpenGL Application.
For more information about selecting the right OpenGL for your development, I would suggest reading "Choosing an OpenGL API Version";