<script type="text/javascript">    
    $(document).on('ready pjax:scriptcomplete',function(){
 
        // Hide the submit button
        $('#ls-button-submit').hide();
 
        // Listener on the (hidden) radio inputs 
        $('#question{QID} :radio').on('change', function(e) {
           $('#question{QID}').hide();
 
// Here you have to adapt the questionIDs of your survey
           $('#question5684').removeClass('hidden');
           $('#question5685').removeClass('hidden');
           $('#question5686').removeClass('hidden');
           $('#question5687').removeClass('hidden');
        });
    });
</script>

<script type="text/javascript" charset="utf-8">
$(document).ready(function() {  // Hide the "Previous" button
  $('#ls-button-submit').hide();
  var vid = document.getElementById("myvideo");
  vid.volume = 0.3;
  vid.onended = function() {
    $('#ls-button-submit').show();
  }
});
</script>