How to change the position of a block in a particular page?
You can place the default User Login block in Sidebar first region at the last position. You can exclude this block from being shown in Homepage using 'Visibility settings' which is available in the block edit page.



Then you can use front page template page--front.tpl.php and render the block manually by passing the block markup through hook_preprocess_page().

function THEME_NAME_preprocess_page(&amp;$vars, $hook) {
  $front_page = drupal_is_front_page();
  if ($front_page) {
    $user_login= block_load('user', 'login');
    $vars['user_login'] = _block_get_renderable_array(_block_render_blocks(array($user_login)));
  }
}


Then you should print the $user_login variable in the front page template inside the Footer Fourth region.