First question: Yes, this game is meant for Adult Audiences there will have NSFW scenes eventually. Since artwork cost a lot of money it takes a while for me to get enough to pay for more art. There is some written content that is very much +18 already.
Second Question: Yes, you need to become a Tier2 patron to access the latest build. You can also suggest corrections with the latest build as long as you give your current Patron Name (username on Patreon) when sending the suggestion, accepted suggestions puts your name in a special list in the credits as one of the Revision team members. And every build on Patreon is compatible with Windows, Linux, and Mac. I can test the Linux and Windows versions, but I already had some Mac users there that assured me the MAC version works too.
On Patreon, you will have a new build every month, usually, the new builds come with new story segments or bug fixes, new features when they can be added, and so on.
And ah, your name will be permanently added to the credits once you become a Patron, even if you help the project for only one month, so remember that. If you want your name censored or removed from the credits you need to report that after you become a patron. :D
Anyway, I hope I have answered your questions properly if you have any more doubts don't hesitate to ask, I'll answer you as soon as I get the notification in my e-mail.