A little walkthrough after painstakingly breaking down the game code to find out what causes what and directs to what. Even checking the directories one by one, it's still a fucking pain to deal with this engine. All they had to do was to allow saving or backtracking and it would be fine, but they make the game unnecessarily complicated. Ok.
The only things that matter significantly to get to the interesting parts are a couple of metrics.
If their relationship reaches green bar (perfect choices) and you have Anna affection higher than 345 = Blowjob scene
If their relationship is blue + you have Anna higher than 255 relationship after the last checkpoint = you can flirt with her / help her stretch out / make out and grope her
If their relationship is blue + you have River higher than 95 relationship points AND don't flirt with Anna (it will reduce River relationship points) = River gets topless and naked by the end, but that's about it.
Depending on the lust points you can get some little scenes with Anna, like getting her topless at the end, but that's about it.
The part everyone was stuck at (first checkpoint) Needs 2 conditions to be progressed. You need to check the empty space on the fridge before picking the water (hint for future questioning of River) and you need to check the orderly organized glasses before progressing (2nd hint).
River's story answers are
Truth - Lie - Lie - (?*) - and Truth (I think the second to last doesn't matter, but just in case you can tell her she wanted to look at herself then say it's truth someone entered the room)
I think those are the only relevant things to know. The rest is getting the stats by trial and error then choosing the options that give relationship points.
* You need to argue with Anna at the first scene to the very end in order to start the game at all or you'll get a bad ending no matter what before the first checkpoint. Just choose the options that affirm you are the captain and know better until she goes away.
- I don't hate this type of game necessarily, but the engine really makes it unnecessarily frustrating to actually go through it.