Idk about the gallery, but for the achievements there's this https://tales-of-androgyny.fandom.com/wiki/Achievements and I was able to find out how to get some of the gallery pics I couldn't find by browsing the rest of the wiki. I do suggest to only activate achievements you've gotten in previous versions (I've had the same issue with updates before) and maybe the story mode one and actually manually doing ones you haven't done.
