I have this code that is supposed to limit the user to the edit of (only) one predefined created custom post type. I want to setup only one post that is responsable to manage the homepage contents. I have an issue, I've noticed that the post type is ceated more than one time, I need that the user can edit only a single post so I've implemeted this:

  function edit_homepage_link()
  {
    global $submenu, $pagenow;

    // query the homepage posts
    $homepage = new WP_Query( array( 'post_type' => 'homepage' ) );

    // if its new post page and we have homepage
    if ( $pagenow == 'post-new.php' && $homepage->have_posts() ) {
        wp_die('You cant add more then one homepage');
    }

    // if we have homepage post, show the edit link else the add homepage link
    if ( $homepage->have_posts() ) {
        $homepage->the_post();
        $link = get_edit_post_link( get_the_ID(), 'return' );
        $title = 'Edit Home Page';
    } else {
        // in case if the user has deleted the default post
        $link = get_bloginfo( 'url' ). '/wp-admin/post-new.php?post_type=homepage';
        $title = 'Add Home Page';
    }
    $submenu['edit.php'] = array( array( $title, 'manage_options', $link ) ) + $submenu['edit.php'];
}
add_action( 'admin_menu', 'edit_homepage_link' );

function register_homepage_cpt() {
    $labels = array(
          'name'               => _x( 'Homepage', 'post type general name'),
          'singular_name'      => _x( 'Homepage', 'post type singular name'),
          'menu_name'          => _x( 'Homepage', 'admin menu'),
          'name_admin_bar'     => _x( 'Homepage', 'add new on admin bar'),
          'featured_image'     => __( 'Featured Image', 'text_domain' ),
    );
    $args = array(
        'labels'          => $labels,
        'description'     => __( 'Personalizza Homepage', '' ),
        'public'          => true,
        'show_in_menu'    => true,
        'show_ui'         => true,
        'menu_position'   => null,
        'capability_type' => 'page',
        'supports'        => array('title','editor','thumbnail','custom-fields','excerpt')
    );
    $post_data = array(
        'post_title'  => 'Home Page',
        'post_type'   => 'homepage',
        'post_statue' => 'publish',
        'post_author' => 1
    );
    wp_insert_post( $post_data );
    register_post_type( 'homepage', $args );

  }
  add_action( 'init', 'register_homepage_cpt' );

How I can fix my issue, is there a way to register and programmatically create only one time a post? Help please. The original code solution is taken from an old answer that I've found here.