The milk farm is unlocked via the main story by completing chapter 1 of Daemonheim.
Mmmh unless I'm missing something, it's possible a variable didn't trigger properly. Try replaying 1-4 and 1-5 without skipping the cutscenes. (the demo version is getting pretty old and we've made several fixes since then so it's hard to remember it all. We should be pushing out a new version at the end of this month though)