Both counts as a post. Starting a new thread is making a post as well as replying in any other thread is a post.

So to answer what I think you really want to know: No, you do not need to make five new topics. You might aswell just reply in 5 topics.

What probably keeps you longer in the newbie area than gettuing 5 posts is the requirement of being logged in for 4 hours, because the logged in time only increases while you are active. Just keeping a browser tab witrh the forum opened in the background will not help you get 4 hours of being logged in.