How can I show a block only on the edit page for a specific content type?
You could implement hook_block_list_alter() to alter the status of the block. (Replace $bid with the block ID, and $content_type with the content type you are interested to.)

function mymodule_block_list_alter(&amp;$blocks) {
  if (!empty($blocks[$bid]) &amp;&amp; ($node = menu_get_object()) &amp;&amp; arg(2) == 'edit' &amp;&amp; $node-&gt;type == $content_type) {
    $blocks[$bid]-&gt;status = 1;
  }
}