Absolutely! The big godling payoff comes to mind, which requires you to have done like 3 random side quests at totally different points in the game, none of which even tell you that godlings are involved until you do them, and even if you do them all, you need to make certain choices in order to get the final result.
Yup, exactly. The yellow ones will progress the conversation into the minimum necessary dialogue to complete the mission, and the others are usually just extra context. I say usually because occasionally there are clues in those sections that will let you make better decisions later on that wouldn’t have been obvious, or even open up new “yellow” options if you keep digging at them.