How can i add a metabox to pull list of custom posts (any two) on edit or add post screen?

I want to add metabox to pull list of custom posts and select any two of them on edit or add post screen. And At last when the post is published display them on single post page. Please help me!
Any help will be appreciated….

    add_action( 'add_meta_boxes', function () {
    add_meta_box(
        'yourcustom_sectionid', 
        __( '👋 Custom Offer Section', 'yourtextdomain' ), 
        function ( $post ) {
            wp_nonce_field( plugin_basename( __FILE__ ), 'yourcustom_noncename' );
            $cstm = get_post_meta(get_the_ID(),'yourcustom_meta',true);
            echo "<pre>".print_r($cstm,true)."</pre>";
            $getPostsToSelect = get_posts('post_type=offers&numberposts=-1');
foreach ($getPostsToSelect as $aPostsToSelect) {
    ?>
    <label>
        <input 
          type="checkbox" 
          name="yourcustom_meta[]" 
          class="postsToSelect"
          value="<?php echo $aPostsToSelect->ID ?>"
         /> 
        <?php echo $aPostsToSelect->post_title ?>
    </label><br />
    <?php
}
        }, 
        'listing'
    );
} );

and then below:

echo "<script type="text/javascript">
  var limit = 2;
jQuery('input.single-checkbox').on('change', function(evt) {
   if(jQuery('input.single-checkbox:checked').length > limit) {
       this.checked = false;
   }
});
</script>";

but the jquery does not seems to work to select the two checked boxes…
and after that problem please help me printing the the two selected checked posts.

the result i obtained till now is with 4 custom posts named offer
in the image shown below

You can add a metabox in the edit screen with

add_action( 'add_meta_boxes', function () {
    add_meta_box(
        'yourcustom_sectionid', 
        __( '👋 Custom Meta Box', 'yourtextdomain' ), 
        function ( $post ) {
            wp_nonce_field( plugin_basename( __FILE__ ), 'yourcustom_noncename' );
            $cstm = get_post_meta(get_the_ID(),'yourcustom_meta',true);
            echo "<pre>".print_r($cstm,true)."</pre>";
        }, 
        'page'
    );
} );

You can query posts with get_posts() and add some check boxes inside that metabox

$getPostsToSelect = get_posts('post_type=post&numberposts=-1');
foreach ($getPostsToSelect as $aPostsToSelect) {
    ?>
    <label>
        <input 
          type="checkbox" 
          name="yourcustom_meta[]" 
          class="postsToSelect"
          value="<?php echo $aPostsToSelect->ID ?>"
         /> 
        <?php echo $aPostsToSelect->post_title ?>
    </label><br />
    <?php
}

You’d than need some jQuery to restrict to only 2 selected. It’d be somthing like

var limit = 2;
jQuery('input.single-checkbox').on('change', function(evt) {
   if(jQuery('input.single-checkbox:checked').length > limit) {
       this.checked = false;
   }
});

You’d save it all with somthing like :

add_action( 'save_post', function ( $post_id ) {

     if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
          return;
     if ( !wp_verify_nonce( $_POST['yourcustom_noncename'], plugin_basename( __FILE__ ) ) )
          return;
     if ( 'page' == $_POST['post_type'] ) { // not the Post Type
          if ( !current_user_can( 'edit_page', $post_id ) )
               return;
     } else {
          if ( !current_user_can( 'edit_post', $post_id ) )
               return;
     }

     update_post_meta($post_id,'yourcustom_meta',$_POST['yourcustom_meta']);
});

Then in your single.php, or wherever your loop is that you want them to show, you’d just call them up:

$cstm = get_post_meta(get_the_ID(),'yourcustom_meta',true);
foreach ($cstm as $aPostToDisplay) {
    echo "<pre>{$aPostToDisplay->ID} - {$aPostToDisplay->post_title}</pre>";
}

Please note that I free handed this (not tested), so copy/paste will not work.. It’s more of a logic guid.

I’ve assumed without double checking that name="yourcustom_meta[]" will pass only the checked ones to $_POST['yourcustom_meta'], but you might want to confirm that.

I’ve also used anonymous functions, which probably shouldn’t be used if this is a for-public plugin/theme.