What is the ruling on studying personal status law that contradicts the provisions of Islamic Sharia in matters such as polygyny, divorce, and adoption?

What you mentioned belongs to corrupt sciences that contradict the rulings of Islamic law and clash with the definitive verses of the Qur’an. Regarding polygyny, Allah Almighty says: "Then marry such women as seem good to you, two, three, or four." And concerning the permissibility of marrying a woman who has been divorced three times after she marries another husband, He says: "And if he has divorced her [for the third time], then she is not lawful to him afterward until she marries another husband." And regarding the prohibition of adoption, Allah Almighty says: "Nor has He made your adopted sons your [real] sons." Learning this falsehood as a form of affirmation is an apostasy from Islam. However, it is permissible to study it to expose its falsehood and warn against it, as Allah Almighty said: "And thus do We explain the verses, and that the way of the criminals might become clear."