Backup moto G firmware without root I installed Cynogemmod on my moto G, but it was android 4.4, and there is no android 5.0 stable version available for cynogen. so I decided to install motog stock framework, I searched on google, but I didn't get any link of original firmware for my motog dual sim mobile.

There is another option I found is copy firmware from my friends moto G. Is there any way to copy firmware from mobile without ROOT, and without unlocking that device?
To answer the question, no. It's not possible to extract firmware without having an unlocked, rooted Moto G.

To help with your original problem, see this thread on xda-developers forum (assuming you are talking about the original 2013 Moto G, and not the newer 2014 model.)  It has step-by-step instructions for flashing stock firmware onto Moto G.  It links to this site, which contains many stock Moto G firmware images for various models, regions, and Android versions.  You have to make sure you are downloading images matching your phone's model and region, otherwise you may introduce incompatibilities and end up with a non-functioning radio.