I'm not a dev, only a tester so I don't know the answer to most of these, and those I can answer take with a grain of salt as I might be wrong.
This is a maybe. Technically also Marlie breastfeeds, just not to you.
No idea.
I believe this is planned as there is already generated art for Amanda with the Main Character, just not canon to the game, yet?
No, not very likely except with the case of Soraya where an ending is that you become her child. It doesn't stick though since you get revived anyways.
I do not know. I doubt it since the character is way more known and is owned by someone else that is also part of a show that is on Amazon Prime Video. Would very likely get the game shut down if she was included. As for Roxy herself, she is not exactly the same as her FNAF counterpart as she not an animatronic, so there's some leeway in arguing she's not the same character. (I'm not a lawyer, and I'm only guessing here.)