8 - How can I detect when an entity is being autocreated?
You need a custom EntityReferenceSelection handler plugin. An example would be how the node module sets the autocreated entity to published:

Drupal\node\Plugin\EntityReferenceSelection\NodeSelection:

  public function createNewEntity($entity_type_id, $bundle, $label, $uid) {
    $node = parent::createNewEntity($entity_type_id, $bundle, $label, $uid);

    // In order to create a referenceable node, it needs to published.
    /** @var \Drupal\node\NodeInterface $node */
    $node-&gt;setPublished(TRUE);

    return $node;


You find more information in the plugin annotation class https://cgit.drupalcode.org/drupal/tree/core/lib/Drupal/Core/Entity/Annotation/EntityReferenceSelection.php