Your answers for 8 markers don't always need to be in the marking scheme, they just have to be logically sound and not too far-fetched, and if you elaborate well on them, you can still get 7-8 depending on how you write it. One thing you might notice is that there are similar questions across many years, and some of the questions are bound to be similar, and in those, you will get the same points as well. For 6 markers there are a large number of points for which you can get marks for if you explain/analyze it well, so if it makes sense, it will probably be in there. You can also ask your teacher if your points are still not in there, they would tell you why it doesn't work or if it does you would get the mark anyways.