Yes. There is creative mode which is a mode where you get infinite items, and can fly around. You can do this by changing the world options before you create a world. There are also things you can download that let you change the mode of worlds you already have.
If you are looking for a easy way to install mods, someone made another Minecraft that can be used for downloading mods easier.
Same way you build a house. Blocks.
You can build anything ! but the best will be to build a auto smelter, Here is a link to the tutorial....
Build a city of your own!
You can build structures in Minecraft by placing blocks you find throughout the game. (MOUSE2 by default)
all you have to do is dig underground and deep in to the place you can make a hidden temple
Go to a site called minecraft wiki
use your creativity... thats what minecraft is about
An easier way to get minecraft would be to type minecraftsp.exe into google and run that. you can get it from mediafire or 4shared
there are none
Build.
You can build your house anywhere you want in the world of Minecraft. One of the best places is to build where you first find coal. Also, try to build in a place that's flat.