Steam requires me to download downgrades as well as upgrades?

[kallisti]

I'm new to this whole Steam thing (made clear by some ignorant comments in other threads), so maybe I've missed something. Today I downloaded and installed the Alpha 13 preview. After discovering that plants went black/away after collisions, I downgraded. This also took a several minute download. When trying to upgrade again, it's the same thing. Do I have to do this each time, or is it possible for me to store these updates locally and switch between them using Steam's Offline mode?

BTW, thanks so much for all the help so far. I'm touched.

[Gordon Freeman]

is it possible for me to store these updates locally and switch between them using Steam's Offline mode?

It may be possible to do this by creating a new account that shares your Steam Library. I'm not 100% sure that this will work, but it seems awfully logical.