yes u do
You can buy minecraft at minecraft.net. First you need to make an account, then you need to buy a premium for that account. Then download minecraft, and login. Now you're ready to play.
You need to buy minecraft but orspawn is free
You can buy Minecraft from the website. The link is under "Sources and related links" below this answer. You currently need a Paypal account to buy the game. You also need a registered username.
$26.95
You need to buy it from the Minecraft's website. The link is under "Sources and related links" below this answer. There it's a button on the right that says "buy now". You need to buy it with paypal.
1600 credits
All you need to do is make an account on minecraft then buy the full version. If you do download it and you don't get the latest version you just use your minecraft password to update. If you don't know the password then you need to make a new account. If you've already bought minecraft and you forgot your password then you can redeem you minecraft gift code to buy minecraft for free. But you can only do this when you've bought minecraft before.
No, you don't need to anyway. You buy it using Paypal or a card at its website.
No. To play together online both of you need to buy the game.
You can buy minecraft gift codes, from the official minecraft website. The link can be found under "Sources and related links" below this answer. You need an account to buy gift codes. Though, creating an account is free.
No, you need to register and pay for the premium account online.
Yes. It's the only way you can get it. I believe you need to have Xbox Live to buy it, because you can not get Minecraft as a retail version, so yes I believe you do need Xbox Live to get Minecraft.