Show certain posts in a page

[abdfahim]

I am following this old tutorial to show a particular post in a page. However, I'd like to know how to

1. show multiple post (let say, posts with id 5,7,8)
2. get the thread link for the post (I know I can get thread_id form the $thread['thread_id'], but this suggestion did not work to build a link)

$ftpHelper = new XenForo_ControllerHelper_ForumThreadPost($controller);
list($post, $thread) = $ftpHelper->assertPostValidAndViewable($postId);