Reverse Query Relationship for Advanced Custom Fields

gistfile1.php

<?php
$posts = get_posts(array(
    'posts_per_page' => 1,
    'orderby' => 'rand',
    'post_type' => 'testimonial',
    'meta_query' => array(
      array(
        'key' => 'related_project', // name of custom field
        'value' => '"' . get_the_ID() . '"',
        'compare' => 'LIKE'
      )
    )
));

if ($posts): ?>
<section class="testimonial">
  <div class="page testimonial__content">
    <?php foreach ($posts as $post):
      setup_postdata($post);
      ?>
      <blockquote class="testimonial__blockquote">
        <div class="">
          <p class="testimonial__quote"><?php the_field('testimonial') ?></p>
          <span class="testimonial__author">-<?php the_title(); ?></span>
        </div>
        <span class="testimonial__image"><img src="http://placehold.it/259x169" alt=""></span>
      </blockquote>
    <?php endforeach; ?>
    <?php wp_reset_postdata(); ?>
  </div>
</section>
<!-- ./testimonial -->
<?php endif; ?>