[Paragraph variables] #d8 #twig

1.twig

{# This paragraph's parent (either a node or a paragraph) #}
{% set parent = paragraph._referringItem.parent.parent.entity %}

{# A field's entity #}
{% set entity = paragraph.field_item.get(0).entity %}

{# Media Library image #}
<img src="{{ file_url(paragraph.field_media.0.entity.field_media_image.entity.uri.value) }}">

2.php

<?php

/**
 * Implements hook_theme_suggestions_HOOK_alter().
 */
function THEME_theme_suggestions_paragraph_alter(array &$suggestions, array $variables) {
  $elements = $variables['elements'];
  $paragraph = $elements['#paragraph'];
  $parent = $paragraph->getParentEntity();
  if ($parent) {
    $suggestions[] = 'paragraph__' . $parent->bundle() . '__' .  $paragraph->bundle();
    $suggestions[] = 'paragraph__' . $parent->bundle() . '__' .  $paragraph->bundle() . '__' . $elements['#view_mode'];
  }
}