Hi @sri
Something like this would work:
<?php
$theatre = $row['theatre_name'];
$theatre = current($theatre);
echo '<li>sub_field_1 = ' . get_the_title($theatre->ID) . ', sub_field_2 = ' . $row['start_date'] .', etc</li>';
?>
Please remember that the relationship will return an array of post objects.
Thanks
E