Yes, that's what they are useful for. One main template with different views (the blog posts) included in it.
Yes, exactly.
By the way single page apps are not always literally single page apps you can have different main templates with views. For example your site blog section may look differently than the portfolio section, but they can both include different views.
you can have different main templates with views. For example your site blog section may look differently than the portfolio section, but they can both include different views.