Here’s what i know, if it helps you.
Spoilers click here
The first you mentioned can be accessed by buying the BIG dildo from the shopkeeper on the starting part of the game and choosing to masturbate with it, you shapeshift into Brianna.Second one i haven’t gotten to it myself but from what i read from the walkthrough if you have low relation with Jake during the prison arc you end up escaping in a different way which is where you can encounter that scene, its a corpse in the prison morgue. So basically be an asshole to Jake at every opportunity you get to get access to this one.
Third one is dependent on what you picked for Demi, if you chose to see Demi as a boy that monster also presents itself as one