Okie!
So there are 4 events for both Sprout and Tangerine. If you get all 4 with either of them and choose the right response all 4 times then you'll reach their endings. (Given you aren't failing your assignment.)
I've updated the itch.io page with the correct responses in order to get their endings.
The order of the events actually doesn't matter, they'll start the conversation based on how many dates you've been on regardless of what you're doing.
Except for one of Sprout's, which is during the Gaming date.
Hopefully that helps!!