You have to create a server and load the map to the server.
Of course you can. Minecraft has a folder with worlds in it in Application Support, so just put the map in.
Yes, it is only a custom map. All custom maps are free, and you should never have to pay to play one.
You can make a custom map on minecraft with out a map editor by building or demolishing certain land features or you can use a seed by typing your seed in the bottom box on the "create new world" menu.
No it is a custom built map
Put the new map in the minecraft_server folder then open the server.properties file and add the name or number of the map next to level-name=.
escuse me but what?
It depends on the map.
SkyBlock is a great map.
-579322790607890076 is the seed and the map is custom
the demo? you play it like you play minecraft just do what it says
to play a map, open minecraft, then click singleplayer, choose the world, then click play selected world.