I don't remember if I got it after beating the game, or if it was there from the beginning, but it's pretty much that big Points button on the top right.
As for Sidney's extra scene, this is what I have so far (WARNING!!! SPOILERS!!!): https://pastebin.com/uWytq3Vr
First of all, let me see that this game is amazing, and the fact that it's not finished yet just goes to show that it's great at what it does. Characters are interesting, and they don't feel shoved into the game.
All of that said, how in the world does anyone unlock the Sidney image on the gallery? I spend like 3 hours resetting over and over trying to figure out how to get 10 points to no avail, always getting stuck on 9. Managed to see his extra scene, but the image just doesn't appear.
