Wordpress - How to get all featured image sizes and their URLs?

I don't remember a function that will do precisely that, but it is easily achieved with API overall:

1. Retrieve attachment ID with get_post_thumbnail_id()
2. Retrieve available sizes with get_intermediate_image_sizes()
3. For each size use wp_get_attachment_image_src(), which gives precisely data you need (URL and dimensions).

After you get it's ID ( get_post_thumbnail_id($YOUR_POST_ID) ) you need to know the uploads base url and the attachment meta data.

Uploads base url can be found in an array returned by wp_upload_dir().

Attachment meta data can be retrieved by wp_get_attachment_metadata().

Here is a handy function I wrote that prepares the url data for any image attachment, not just featured.

function prepareImageData( $attachment_id ){
  $uploads_baseurl = wp_upload_dir()['baseurl'];

  $prepared = [];
  $data = wp_get_attachment_metadata($attachment_id);
  $prepared = [
    'mime_type' => get_post_mime_type($attachment_id),
    'url' => $uploads_baseurl.'/'.$data['file'],
    'sizes' => [],
  ];

  foreach( $data['sizes'] as $size => $sizeInfo ){
    $prepared['sizes'][$size] = [
      'url' => $uploads_baseurl.'/'.$sizeInfo['file'],
    ];
  }

  return $prepared;
}