Are flipping underwear, contracting marriage at the end of the Hijri month, not leaving the house, and avoiding seeing a barber or a menstruating woman for someone who wants to document a marriage contract, part of the religion?

These customs have no basis in Islamic law; they are reprehensible practices stemming from ignorance and superstition. Therefore, beware of following them and adhere to the Sharia (definition). To protect yourself from magic, the evil eye, and similar things, maintain the prescribed remembrances (adhkar) and the legitimate incantations (ruqya). Our advice to you is to learn the rulings of Islamic law and act upon them, especially in matters of marriage.