For the category list, which is /categories, the template is categories.
For the home page, it depends on which page is your home page. Most likely it is the qa template that displays the "Recent questions and answers".
Anyway, you can find each template yourself. Just open your qa-theme/<your theme>/qa-theme.php file and add/merge this function.
public function initialize() {
parent::initialize();
echo $this->template;
}
You should just see the output on top with the template for the given page.