Get menu names and same depth level menu names

Sorry, this is a little vague but it should get you started. It seems like you need to:

1. Check if the page has a parent <?php if($post->post_parent) ?>
2. Something like <?php echo $post->post_parent; ?>
3. Something like <a href="https://wordpress.stackexchange.com/questions/113592/<?php the_permalink() ?>"><?php the_title(); ?></a>
4. Something like the code below, then apply your solution for turning it into a dropdown.

There is more info here: http://codex.wordpress.org/Function_Reference/wp_list_pages

<?php
  $children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
  if ($children) { ?>
  <ul>
  <?php echo $children; ?>
  </ul>
  <?php } ?>