One thing I can say pretty certainly is that Boundless, due to how it is developed, does not do hovering drop down menus. You might be better served looking into a different theme entirely.
If anyone can correct me, I'd be happy to hear. :) But just so far in my experience it is not possible - or at least not easy to do.
Unfortunately, dropdown menus aren't native to the boundless theme. I've made a tutorial explaining how to implement contextual menu functionality on every page of your site using boundless:
Hope that helps!