Drupal Node view modes
If you would be okay with having a parameter in the url control your view mode then you can add this code to your custom module using hook_entity_view_mode_alter(). 

For example:

http://www.yoursite.com?view_mode=Full

http://www.yoursite.com?view_mode=Teaser

.....

/**
 * Implements hook_entity_view_mode_alter().
 */
function my_module_entity_view_mode_alter(&amp;$view_mode, $context) {
  // If there is a view_mode parameter in the url change the view mode to it.
  if (isset($_GET['view_mode'])) {
    $view_mode = $_GET['view_mode'];
  }
}