If you're talking about a Minecraft world, there is no limit. The world keeps randomly generating. If you're talking about the map item, it changes. As of 1.4 you can expand a map to make it show more blocks.
Same way you build a house. Blocks.
On PC, it is infinite (or until Minecraft runs out of memory).
It depends where you stand. Mountains, seas and regular plains will all have different block levels. On your Minecraft map you will see x, y and z coordinates. Y is the number of blocks you are above the bottom of the earth. Y:12 is the 12th layer.
For single player, maps can be extracted to %appdata%/.minecraft/saves. For multiplayer (provided you're the host of the server), maps should be extracted to your server folder, with 'server.properties' edited in Notepad to reflect the world map's name.
Yes - and the location is different in every map. It will generate between 640 - 1152 blocks (in both the x and z) and the numbers can be negative as well, for example, x: -1100 z: 800
Either go into the single player menu in Minecraft and select which one you want or add the map/world into your "saves" folder. If you want to add maps to your Multiplayer then just put the map into the folder your server app is in then add the name of the map into the "server.properties" folder for the game to see it.
Locate your Minecraft folder, then find your save file. Copy and paste this onto your hard drive. Minecraft is installed in your AppData folder (C:\Users\[username]\AppData\.minecraft\) The saves folder should be in the .minecraft folder.
After you log in, select Single Player and select "Create New World" to get a new random map.
if you would bother to count yourself its 13 dirt blocks used to make the map.
Some might, but an adventure map is a MAP, not a mod. Just search for "adventure map" on Google or the Minecraft Forum.
Herobrine's Mansion is a popular Minecraft map rather than a server, and it can be played on single-player or hosted on a multiplayer server. Players often share servers that host this map, but specific server addresses may vary. You can find servers that feature Herobrine's Mansion on platforms like Minecraft Server List or similar websites, or you can host the map yourself. Always ensure to check the map's compatibility with your version of Minecraft.