B - was set in stone from day 1. Surprised at how many people bought the fake-out of the last few chapters, thinking it's never going to happen. Holly's practically a third MC and this is most definitely locked in.
A - is almost locked in too, based on a few convos that are presented depending on the paths you choose. It's just a more side-track path to get to it.
G - Practically happened already. About as likely as A, maybe more.
F - Technically, it's not a threesome if all the dirty old man does is watch and take pictures. That'll happen, but almost definitely the most the old bastard will do is stroke himself while commanding them, if even that...
Actually, I could see Seymour commanding Lena to lather his testicles clean with her tongue or to suck him off while he
commands Axel (or hell, even Ian) to fuck her hard. But with the specification that she must not, under
any circumstances, use her hands or touch him (Seymour) in any way. Mouth and tongue alone. He may or may not grab her hair and control her depth with it. Edge case though and I wouldn't bet on it. One thing I'm sure of is if there is any physical contact with Seymour, it won't be anything like a standard threesome.
The rest are a crapshoot based on time limits of Eva's development cycle. Some much more imaginable than others.
Not mentioned but 100% happening: Billy, Lena, Jeremy.