I suppose v1 and v2 are the simplest versions but as much as simple the more difficult they are. I've heard the v4 is more difficult than v4.5 but I don't know if v3 is more difficult than v4. I know v5 seems to be easy to the point it got too boring to me. v6 seems to be the hardest to me and I believe v5.5 is as difficult as the v5. What do you guys think?