A Linux, Windows, or a Macintosh.
Yes you can, but you need to download minecraft for macs
You need a password, it's the same password as your Mojang or Minecraft account.
no you can not
You may need to download the newest version of Java for minecraft to work. Or maybe your computer can not handle it.
Minecraft is all about the account you made, you can log into that account on any computer, you are not forced to play it only on the computer that you purchased it on.
In a sense, yes, but in another sense, no. You do not need to install Minecraft to play it on a computer, you can simply run it in your internet browser on Minecraft.net. However, if you want to run Minecraft without an internet connection, or without visiting Minecraft.net, you must install Minecraft on your computer. You can install Minecraft on multiple computers under the same account, but your saved worlds will not sync between computers.
No I dont think so it depends on what kind of computer.
Yeppers.
Play the game
Yes, simply download it from the minecraft website.
you just have to download it on the computer you want that minecraft to be
obviously its amazing for ur computer if u play minecraft ur the best! :D