You use the launcher to login to your account, and it downloads all the files for you!
Yes it does. Though on occasion Minecraft will crash and you have to set it up again.
Watch youtube videos.
you cannot set up permissions in a normal minecraft server. you must have a bukkit server to use permissions. check the bukkit forum for more info.
In order to play Minecraft with friends, you need to set up a server. You can either set one up on your own computer, or you can rent one from a company for fairly cheap prices.
Registering for Minecraft is free, it just set's you up for buying Minecraft. $26.95 US is how much it cost's.
Use the hamachi server.
There are tons of tutorials out there. If you are running Minecraft Beta 1.8, you should update to the newest version.
Minecraft Wiki has a complete guide. The link can be found under 'Sources and related links' below this answer.
Realms is an in-game feature that allows players to set up their own servers without having to look outside Minecraft for a web host.
You can set TNT off in Minecraft Beta by clicking it, or by triggering it with redstone.
You need the server software first. Once you get the server set up, you can copy your save to the server.
You need to download a bot. Search for one on the Minecraft Forums, or a search engine such as Google. Then when you have one you like, follow the instructions on how to set it up.