Function to get a list of all comments on 1 post [closed]

You should use get_comments( $args ) and add the post ID in the arguments ($args) array:

$post_id = 1; // post ID here from the submitted data
$comments = get_comments(array( 'post_id' => (int) $post_id ));
// dump the comments found
print_r( $comments );

That would get you a comments list on that post. Hope that helps.