There is only one version of the game, but 3 expansions. You must upgrade in order of expansion, up to the latest, you want to play all of the content/races available.
Warcraft
no, it should automaticly become the full version
If you do not have the install disc for World of Warcraft, then yes, you have to download it and let it update to the current version.
no unless you get the illegal version
That should be a key code that you need to enter so you can activate the version of WoW you bought.
Yes, there is a version of World of Warcraft for Mac OS X on Intel processors.
The world of warcraft client is auto updating, meaning it should automatically update itself when you try logging in. If the auto-update is not working, then something is wrong and you might need to call blizzard technical support for help.
There's Warcraft III and its pretty much like the MMORPG version.
World of Warcraft is a subscription based service and is only free to play with the trial version for 10 days.
Are you asking for the best Warcraft game? Or the best battlegrounds in World of Warcraft? If the best Warcraft game, then single player: III, The Frozen Throne. If you mean battlegrounds then I think Arathi is more fun than Warsong and Alterac Valley.
When World of Warcraft is installed, it asks you if you want to install Direct X.(only if you currently have a previous version)
World of Warcraft is listed as compatible with Windows 7, and should work fine.