Currently, what are the differences between the demo and the Patreon ver game?
The demo won't have any content past chapter 1 of Daemonheim + Radian.
Currently, the patreon version has a part of Dregan which is 3 more characters worth of story, stages and scenes. This will soon be 4 characters with the entirety of Dregan complete (the last update for Dregan should come out at the end of this month)