the new version of minecraft is called tekkit. i think it allows you to build machines and vehicles.
(Tekkit is actually an Add-on and isn't created by the makers of Minecraft. I'd suggest reading up on this mod before downloading because some mods will delete saved game data if not installed properly.)
Mojang does not sell previous versions of Minecraft. If you have a Minecraft account, download a mod which allows you to play previous versions of the game.
You can download "Minecraft Nostalgia" to downgrade versions of minecraft
The different minecraft versions are incompatible.
The newest version of Minecraft as of October 4, 2015 is 1.8.8, but the newest snapshot of Minecraft is 15w40b
No. You cannot connect with other players with other versions.
Good seeds vary between different Minecraft versions.
There is no time machine in minecraft. The "Time Machine" is a nickname for the Minecraft Launcher, the startup of the game. You can access old versions of Minecraft.
Cracked versions can give you viruses depending on what website you use.
You can't. You can, however, mine it in the snapshot versions of Minecraft 1.5
You can start a game on a totally flat world, in the latest versions of Minecraft.
You just re-download Minecraft, force update it, or update it if it gives you the option.
There are no apple trees in any Minecraft versions, but in the latest update of Minecraft for Xbox apples drop from tree leaves.