Is it permissible to pay the Fitr Zakah (obligatory charity) of Ramadan on behalf of a dead person?
The Fitr Zakah of Ramadhaan isn`t due on one who had passed away before the sunset of the last day of Ramadan. And Allah Knows Best.
Is speaking to a person from the opposite sex forbidden or not?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Talking to a person from the opposite sex is forbidden in Islam because it entails a great deal of evil, which could lead to a graver sin. Moreover, Islam forbids having a friend from the opposite sex. And Allah The Almighty Knows Best.
Is it permissible for the doctor to uncover the hair of a female patient out of necessity?
It is only permissible for him to do so when there is no female doctor, and he should examine the patient in the presence of one of her Mahrams (unmarriageable kin).
What is the ruling on reciting verses of the Holy Quran on water, then drinking it?
It is permissible to recite Quran on water, then drink it as a kind of treatment since the Quran heals. Allah, The Almighty, Says (What means): "We send down (stage by stage) in the Qur’an that which is a healing and a mercy to those who believe: to the unjust it causes nothing but loss after loss." [Al-Isra`/82].