Display selected values with summary from dropdown control

Question

I have a dropdown select (country_project) with some countries in a custom post type (project). You can choose 1 value. I want to create a comma-separated list with all values chosen in all posts, once. Non-chosen values are not displayed. So the script should echo:

France, Japan, Maroc, Australia

And for the same list, I want to have the number of different countries chosen. So in the example above the output now should be 4.

So I can create something like:

There are 4 countries presented: France, Japan, Maroc, Australia

How do I do this?

Almost too embarrased to share, but this is what I got so far. With this I thought to create the list with the selected countries in all posts and display them by their name. If I will get this to work, I will see if I can get a number out of that as well. step by step. But as you all probably will understand, except me :) this doesn't work.

 $args = array(
    'numberposts' => -1,
      'post_type' => 'project',
);

$list_countries_projects = get_field( 'country_project' , $args );
 if( count($list_countries_projects)){
                            foreach($list_countries_projects as $k=>$list_countries_project){
                                            if($k) echo ', ';
                                                echo $list_countries_project;
                                            }
}