I think is possible play Robert path without Lena get so into him, at least in the old version. In my old cannon save, Lena started fuck him just to get over Axel, and the sex is always quick and some kind boring (just picking the choices that end the scene quickly) and she never agree in make more kink things with him, like blowjob and sex in the restaurant. Then, once she start have sex with Ian, i just make her choose Ian above Robert and ignore him every single time.
Finaly, after she leave the drawing session with Ian in ep 7, when Robert come to her house to apologize i make Lena dumped him, but not before Lena gave Robert another chance for they continue hooking up and the douchebag blew it spectacularly because he can not stop his bullshit and boring talk about want a relationship with Lena. What a idiot.
Maybe with some head canon, anything is possible. Of course, Eva's coding is among the most complex for a VN styled porn game. Anyone who looked at the script file for this game or GGGB will know just how much variability there is depending on the choices. That said, I do feel like ORS is not as flawless as GGGB in terms of making every conceivable route internally consistent. There is just too many moving parts here. The potential is much greater than GGGB in terms of creating this mosaic of shifting and interconnected narrative pieces, however a closer look may lead to some combinations of choices not being supported sufficiently in the narrative. Some things will just slip through.
For me, the conditional bits of flavor text need to paint a reasonable picture of the mental state of characters. In GGGB, Eva really did address almost any contingency with a generally consistent mental state for Ashley. Honestly, even just the "because drugs" excuse at least gives you enough justification for her to do something outlandish. She also has quite a bit of thoughts about betraying Eric or just basically about any weird situation.
So far, what I'm seeing in ORS is that the narrative relies a lot more on the players creating their head canon and applying their interpretation for the motivations for some of the actions. It also falls largely on the players to pick reasonable choices. A specific example I'm seeing currently in my run is like this. I did everything to get the most points for Lena and Ian to get them together ASAP. They are not official, but it's getting damn close. They've had sex, went on multiple dates, and connect on an emotional level unlike with anyone else. Then, she can go to the club and literally seduce Mike like a slut and get creampied. She thinks about her sex with Ian for one line throughout the whole interaction. It kinda makes no sense that we get no justification whatsoever for her being able to act this way other than making our own head canon. Right after this occurance, she goes on another date with Ian where she can talk about the reason she broke up with Axel in some heartfelt exchange. Girl, you just got creampied by some random dude who has a girlfriend and got off on the fact that you were being a homewrecker. My head canon is basically that she is going to be a despicable hypocrite, so I can make my own narrative, but these are the kind of things that would have been addressed in the script in GGGB.