Is buying shared land from someone who has taken possession of it considered halal or haram?
The shared land is possessed by the country i.e. for all people; therefore, it shouldn't be possessed/occupied save by it's guardian/owner permission,thusly it can't be possessed save by having owners' permission. Finally, buying it from a person who don't possess it is impermissible. And Allah Knows Best.
Is it permissible to pray with a heater (stove) in front of me?
There is no harm in praying with a heater in front of you, as long as you do not intend to venerate the fire or imitate those who worship it. And Allah Knows Best.
Is the marriage, which lacks a valid legal contract, a guardian, and a court registration, valid?
It is incumbent that a valid marriage contract be concluded in the presence of a guardian and two trustful witnesses, and it should be registered in the court to protect the rights of the wife. Actually, a valid marriage contract is what differentiates between sound marriage and fornication.
What is the ruling of Sharia on a Muslim woman who committed Zina with a Christian and became pregnant as a result?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
Abortion is forbidden in Islam as it entails taking the life of a soul unjustly. Rather, it is one of the major sins; however, it is permissible only when there is well-established danger on the mother`s life; in which situation scholars gave priority to her life over that of the foetus, since this is, according to Sharia: "The lesser of two evils". In case a Muslim woman committed Zina (Adultery) with a Christian and got pregnant, if this did happen, then this question should be presented to the Iftaa` Committee with the presence of the questioner herself. She could also ask a reliable scholar face to face or via phone. If she gives birth to the baby, then he/she is a Muslim and takes the name of his mother; not the name of the man who was a reason for its conception. And Allah The Almighty Knows Best.