Hi Friendly :)
Yep, this is a limited beta. It will, of course, become a full version when we release properly. As long as you want to play on PC (not PS4) you definitely won't need to buy another copy on release. As per any beta thing, if you'd rather play the fully polished version, it's best to wait.
We're use the itch desktop app for auto-updating. You should be able to download the game from itch without the manager, but I'd recommend against this as you'll miss out on auto-updating. We'll be patching/improving things a whole bunch, and it'll be worth staying up to date.
We wont be putting builds onto Steam until we release; you _will_ get a Steam key at that point.
I don't have a full list of the statistics we send to hand, but they are solely game related things "which world you died on", "what killed you", "what was the game seed" things like that. We're taking these so that I have more information to help balance the game.
Cheers,
Jonathan