Right now, there’s only one threesome scene available, and it’s with Willa and Anica. It works exactly like you said, you have to get them to follow you and head to the bedroom. But it’s important to mention that the chances of triggering the scene are completely random, so it probably won’t pop up on your first try
The farm and Aunt Nora are Patreon exclusives
Skills don’t cost any money. Your money might disappear because of a bug, but don’t worry, so far there are no consequences for having 0 or even negative money