For your two Molly scenes you have to watch the class then say you need her help, when you go out to the hallway say you want to do more. You'll go to a bathroom and have sex. For ease of getting both scenes make a quick save when asked if you wanna fuck her ass or pussy cause both count as different scenes

The two Linda & Olivia ones are from the holiday event. For the friendship route you gotta go through your living room either in the afternoon or at night and you'll start that, as for the solo route I don't quite know that one yet but will come back once I do

Your missing Lilly scene is a side event that takes place at night, your mom will randomly say she has to go work a shift and wants to get you a baby sitter, you need to chose Lilly.

And your missing Brittany scene is a random event as well. I believe you have to check her bathroom during the afternoons and she'll be showing.