It is probably answered elsewhere which I am unable to find.

My question is simple:
How do you even go about obtaining these beta's and proto's?

I am making my own games and I would imagine most companies keep their stuff in a vault of some kind (yeah I am stretching it lol)

What and how do you go about obtaining a beta or prototype?
I am not asking for any nor do I intend to buy any but I am curios.