no. hard disk has nothing to do with grapihcs. but a 20 gb playstation has less features than a 60 gb playstation that's because the company made it like that. hard disk is just concerned with sroteage.
No, the most important part of Minecraft is a premium account which needs to be registered online. Since the client program itself is only tiny, there's no real point selling it in disk form, you can get it online after registering your account.
No a dlc is short for downloadable content which adds extra things to you minecraft such as on the 360 edition skin packs are dlc content and a CD is something for storing date on or is comonly know in minecraft as a music disk