Override function qa_get_request_content() and redirect to home page or 404 if request is hot or whatever page you want.
Something (but not exactly) like below
if($requestparts[0] === 'hot') {
qa_redirect_raw(qa_opt('site_url'));
}
I have tested and it is working fine. It is redirecting to the home page. You also can use qa_redirect() instead if you want to give parameters instead raw URL
See here how you can override function http://question2answer.org/overrides.php
Edit:
If you want to redirect or block multiple pages than add those in array and check with in_array() function.
I am sure there may be other ways too but I found this way at the moment. If find more than will share here.