Figured out how to unlock the gallery!
Open Growth Academy's folder, then go renpy > common and open up the file called "00gallery" (I use Notepad ++ and you'll wanna make sure it's the RPY file and not the RPYC file). You'll find a line here that says "if not renpy.seen_image(i): return False" and all you wanna do is set that "False" to "True" (without the speech marks, ofc). Annoyingly, this only unlocks all of the images set as "sfw" and I couldn't figure out what to change in "00gallery" but I did find out how to unlock everything else.
Open the Growth Academy folder and then open the "game" folder. In here, find the file called "script_gallery" and open it (again, make sure it's the RPY file and not the RPYC file). In here, right at the top are all of the scenes available for each girl and this is where they're tagged. You'll need to change each image to be tagged as "sfw" and then they'll all be unlocked. I just did ctrl + F and then replaced all instances of "nsfw" with "sfw" but idk how this will impact the game, so be warned that this might mess some things up (Aida, the pregnancy girl or PRG as she's referred to in script, has a few images tagged as "custom" you'll need to change as well).
And you're done! If you don't want to go through all that, I'll include the edited files here, just back your own ones up before changing them. All this does is unlock the images for certain scenes like kissing and sex etc, you don't experience the actual scene so you'll need to play the routes organically to experience those