Tizen Developers

As per the Tizen app design guidelines, the back button functionality needs to be supported for navigation.

If the user wants to return to the previous screen, he or she taps the Back key (hardware key on the right bottom side) or if the user is on the home screen (first screen) of the application, the app should exit.

You can use the below code, but this works only on 2.2 image, as the hardware buttons are handled from 2.2 only. So it's better using the latest SDK 2.2.

// add eventListener for tizenhwkey
    document.addEventListener('tizenhwkey', function(e) {
        if(e.keyName == "back") {         
            if ($.mobile.activePage.attr('id') === 'main')  // "main" here is the apps home page "id".
             {
               tizen.application.getCurrentApplication().exit();
             } else {
               history.back();
             }
         }
    });  

I would also suggest to write in “My Q&A” under Support section in Tizen store for any further app store related queries.

Yeah, as your application doesn't have the BACK functionality implimented , it was rejected. As mentioned above just add the code to the project created on Tizen 2.2 SDK and that'll work.