How to get the latest post list (of the parent custom custom type)

First off, adjust your query so you’re only returning top level posts (the parent posts in this instance)

add_filter('pre_get_posts', 'only_top_level_posts');

function only_top_level_posts($query) {
    // wrap some conditional statements around here so it doesn't affect every query, just limit to whatever queries you need it in
    $query->set( 'post_parent', 0 );
    return $query;
}

This will return only the top level posts.

Then, inside the loop, you can use either get_posts() to get the children of said post (returning the most recently posted):

$args = [
    'post_parent' => $post->ID,
    'posts_per_page' => 1,
    'orderby' => 'post_date',
    'order' => 'DESC'
];

$children = get_posts($args);

or use get_children(), which works in a similar way to get_posts() with similar arguments. Once you have your child post, you can output whatever you need to from it.

Either one of those approaches will return an array which you can then pick apart to get the information you need.

Hopefully that gives you something to start playing around with, I’m sure there’s more than one way to do what you’re after but that’s how I’d start to approach it.