Hi. I have a window 8 and I found some world that was cops and robbers and I really wanted to play but it was only single player. I really wanted to play with other people and I found your .com. I hope you can help. My whole family tried but didn't work.
Most worlds should be able to be played in multiplayer if you open the game to LAN or put the world on a server. As you've found though, some that are intended for single player use can be a bit buggy when played in multiplayer mode.
There's really not a lot you can do to fix that since that was the way they were intended to be played, the problem is in the way the puzzles or activities were built and the world was set up. It sounds like possibly the cops and robbers one you found is one of those.
So you can either play it in multiplayer and work around the bugs, play it by yourself or look for another similar one that works as a multiplayer (there should be quite a few other cops and robbers type ones out there).