Now when I want visit unpublished post page by direct URL like http://.../?p=123
I see 404 error page. Where in code I must to perform fixes to show posts for all guests and visitors undependable from post status.
In case if you wish to do it manually without a plugin.
Goto Wordpress>wp-includes
Open query.php in a text editor
Search for something like $status = get_post_status($this->posts[0]);
Replace it with $status='publish';