Was the Prophet Muhammad (peace be upon him) a polytheist or an infidel before his prophethood, and if not, how was he a Muslim before Islam, taking into account that the Sunnis believe that his father, Abdullah bin Abdul Muttalib, is in Hellfire?

The Prophet, may Allah bless him and grant him peace, was a Muslim believer from birth, as evidenced by the Hadith: "Indeed, I am, with Allah, in the Mother of the Book, the Seal of the Prophets, even while Adam was still kneaded in his clay." And he was born a prophet; his prophethood was incumbent upon him from the time the covenant was taken in Adam's loins, even though his advent into the world was delayed.