Max is 4* with Linda, you get 4* when bob comes to your room (end update). When are alone in bedroom with Linda you will hear footsteps and you will have option what to do then save game, after that do whatever you want and save game on other slot. Someone said maybe choice of this will have different story in future updates.
I mean it ends in two very opposite direction, unless he renders that decision meaningless by having Bob figure it out the moment the next patch starts. 'cause the reaction from both paths are opposite, in one he's obviously pissed off, in the other he's happy for you, so unless Linda does something immediately after leaving your room...
That being said that would be a new one for Icstor, wouldn't it? I've played every single of his game and they're all very linear story and straight forward. I think he experimented with alternate scenes in Milf's Control and Incest Story 1, but it had no impact on the story, you'd just get Scene B instead of Scene A but the rest of the story would unravel in the same way, so maybe this is another one of those. Linda could convince Bob that this was all a dream, or Bob figures it out anyway after leaving your room.