On CubeCraft I have noticed that only one game can be played in 1.8. This is really annoying for players who like to try all the games in one session. For the PvP you can't be in any version higher than 1.8 or you get destroyed. This means you would have to leave and relaunch minecraft to have a chance. There should be a 1.9 PvP server where 1.8 can't join.