is the itermediary in the transformation from an embeded conditional into a joint sufficient conditional a conditional conclusion in the previous lesson?

is 'the only ' here in q2 be understand as all? the overinclusiveness of 'only' really confuses me

@SavanahHoffstein thanks！

In q3, can which be interpreted as a modifier? Is is a little bit confusing about a modifier and a referential, is there an overlap?