Hi Kapree - You can definitely graduate in four years and stil explore different areas of psychology. The first courses you take will be the most general introductory courses, which cover a broad variety of topics. Depending what you find the most interesting, you can then select courses that focus in on those topics. Furthermore, you topics you're interested in are related, i.e., they are not necessarily in different arenas of psychology, which means you might very well find classes that cover multiple of these topics.
You say that you want to be certified in these areas - I'm not sure what you mean by this, but how much time you spend in college does relate to how you want to do with psychology. There are many different psychology-related professions, and they require different types of training.