dota2

Nothing. The world has ended, sorry.

You can't play dota 2 if you don't have key :)

Now you can only try to trade something for an invite or buy one at the store.

thats how the cookie crumbles

Buy a beta access or wait for the release.

or if it works try to add game to wishlist and resync

You could play LoL until Dota2 is officially released.

It's more friendly to beginners anyway (in my opinion) - but then again I don't know how much experience you already have with MOBA games.

Maybe you should have read the description. Dota 2 isn't out, just the Spectator Mode.