Is it sufficient for a father to pay Zakat al-Fitr in money on behalf of his son without his permission, and what is the ruling concerning previous years in this case? And is it considered valid for the son to give rice as a make-up (qada’) for Zakat al-Fitr for the past three years, and is he required to make up for the remaining years, and for which period precisely?

It is obligatory for a father to pay Zakat (definition) al-Fitr on behalf of his minor child. As for an adult, his maintenance is not obligatory upon his father. However, some scholars are of the opinion that whoever voluntarily undertakes the expenses of a person in Ramadan (definition) is obligated to pay their Fitr. Your father's payment of Zakat al-Fitr on your behalf, with your knowledge and approval, is considered an customary authorization, which is sufficient for its validity. Therefore, you are not required to pay it for the past years after you reached adulthood. It is permissible to pay Zakat al-Fitr in cash and to give it to a trustworthy charitable organization that undertakes its distribution to those who are eligible.