What should I do to unregistered users can not access if they know the URL pages? Pie register form only blocks the main page but not the rest of the subpages
This is out of PR scope, however, one can easily manage this if they know programming. You can create a function in your theme’s functions.php that checks for the logged in users if not then redirect to a specified URL. Simply hook this function into the appropriate WP Hook and you’re done.