Custom maps? You will have to setup a server, download the map and replace "world" folder with the custom map (Must be renamed to "world".)
Or you can play on my server and we can set something up. I will setup world file and all that. Just tell me the map and your IGN! (In game name.)
email me at: dave_robertson@mail.com
Chat with our AI personalities
You can't. You can play other games like it. But not minecraft.
Yes, they can play together on a LAN game, but Mineshafters cannot play any real Minecraft games
Create a server.
No, you can't.
You need a premium Minecraft account to play online with other people.