Faculty members don't like to assume leadership of senior projects when the student hasn't demonstrated success in relevant courses. Rather, it will be based on that one introductory course you took with the professor. Talk to your advisor about the best strategic course for you. It often depends on when you declare the major, how many applicable courses you took in your first year and how many all college distribution requirements you have outstanding. There is no perfect path.
Policy is a little trickier.
Some international majors at other colleges are international relations majors. This major focuses primarily on economics and government foreign policy courses and would correlate broadly with the first kind of policy course. If the course deals with international systems or relations between countries, it is usually policy. However, in our major we also consider some of the emerging transnational issues that don't neatly fit in the traditional international relations box. Therefore, courses dealing with gender, the environment, globalization and other critical issues are usually classified as policy.