how to get all options values of simple hierarchical select in drupal $form?
In Drupal 7 you can use field_info_field(), while in Drupal 6 you can use content_field_instance_read(), which is defined in the CCK module.

You can also use list_allowed_values().

$field = field_info_field('field_name');
$allowed_values = list_allowed_values($field);