Every line of "What If?" is a question, and that's the point: the speaker is stuck in a loop of possibilities and can't settle on one. The first half imagines escape. Walking away, saying "I love you" once and going quiet, even pretending not to care at all. But the speaker keeps testing these ideas, asking what it would mean to say "Whatever" and truly mean it. That suggests they don't, and the indifference is more of a shield than a real feeling.
The second half drops the armor. The speaker admits they might love and care, then worries the other person will just stare back. The last four lines turn toward the other person's side: maybe they feel the same but the words won't come. The mood is anxious and tender, full of hesitation. Nobody in the poem actually does anything. The fear of speaking, and of not being answered, is what the whole poem is about.