How can God's mercy, which surpasses a mother's mercy for her child, be reconciled with His not forgiving shirk (polytheism) and the eternity of polytheists in Hellfire? And why did God create polytheists when He was able to create them as Muslims? And is religion a product of the environment in which a person is raised?

Islam does not link a convert to their relatives. Whoever fulfills the pillars of Islam is a Muslim, having the same rights and obligations as other Muslims, even if their parents are disbelievers. This is based on the Prophet's (peace be upon him) saying: "Whoever testifies that there is no god but Allah, faces our Qiblah, prays our prayer, and eats our slaughtered animals, then he is a Muslim, having the same rights as a Muslim and the same obligations as a Muslim."