At the bottom of this thread OP, there are instructions for how to install a persistent file, since to my knowledge there is no easy or good way for Android users to install mods.
By installing the persistent file, it will fully unlock your gallery but also reset your settings, seen text, and also New Game+ unlock status. It will not affect your save files. Unfortunately, unless someone can give me a better (and simple) method of unlocking the gallery for Android users, it's the best I am aware of right now.