Alpha and beta

If u buy the alpha would u need to buy the beta when it comes out?

No. You only need to buy the game once. The key type listed in "MyKeys" is simply to indicate when your access starts.

Even if u buy the alpha off steam ?

Yes. You get the whole shebang. You're paying $70 - they're not going to make you pay again after that!

Confirmed multiple times by the Devs. You've bought the game, including Alpha, Beta and Retail. No need to pay three times.

Unless you want multiple keys, and want to donate more money to the development process.