What's the point of 2.0? Is it optional to have 2.0 or do you have to have it because I don't really like it. Why did they make it in the first place?
Minecraft 2.0 is an April Fool's joke, in a similar vein to the Steve Co. Supply Crate. It consists of a pair of server and client JARs that were modified to have the features shown; this allowed for distribution to select members of the community.
I believe it is not intended to be publicly released.
Minecraft 2.0 comes in three flavours: Red, containing super hostile mode; Blue, containing the new mobs and blocks; and Purple, containing every change. These download links were available for a period of time, but the access permissions have since been changed, making it no longer possible to officially download Minecraft 2.0.
If you really want to play Minecraft 2.0, the Purple (and possibly Red/Blue) server/client JARs have been released by the Content Manager of the Minecraft Forum