Hey Drews!
Firstly, thanks for supporting the game! We greatly appreciate it o/
The content is available depending on where you are in the main story and individual stories of the girls. So it might be a bit before you see content that was introduced in the latest update, for example. You just continue with your save, which carries over automatically whenever you download a new version of the game.
Unfortunately the persistent file and the gallery, when carrying over/backing up, can be really finicky sometimes. You may have to replay from an earlier save or new game to get those back into the gallery.
The gallery is not Patreon exclusive, however the code to unlock it is. The content in the gallery is unlocked by playing the game and experiencing scenes with each of the girls. Some girls might have more scenes than others.
I hope this answers and clears up any questions you had!