Does listening to classical music enhance infants' intelligence?

No evidence for this. Classical music is wonderful, relaxing and exciting at times both recorded and attending live concerts (nothing like it). But there is no proof that your creativity or intellectual capacity will be altered. You might extend your creativity to newer areas while relaxing with classical music and it might stimulate alternative thinking. Your infant may sleep better with it but it will not be smarter.
No. There is likely no difference in the intelligence of babies who listen to classical music, compared with those babies who do not listen to classical music. On the other hand, listening to music will help develop the parts of the brain that appreciate rhythm, pitch, and melodies . . . But the music can be any type that makes a baby smile (not just classical music).
No. Early studies showed that there may be some benefit to exposing your baby to classical music early on, but, for the most part, those studies have been rebuked. It certainly won't hurt your baby to hear beautiful music or to view magnificent art, but unfortunately, it's not a sure-fire way to make them smarter.