Conditions for the validity of Nikaah

Q: If a man and woman commit zina before getting married. After their marriage, they had children and realized that what they have done before marriage was a sin. But they do not repent when being married because they dont have knowlegde that before marriage they had to repent.

After 6 years they got to know that they should have repented before nikaah, otherwise their nikaah is invalid. Is their nikaah valid or not as they repented after 6 years of marriage.

Q: If a girl and boy considers each other as husband and wife without proposal and acceptance, will their nikaah be valid or not? I saw in one tv program, there was female advocate who said that it was the opinion of Imam Abu Hanifa that if a man points to a woman in a gathering in front of many people and says that she is my wife and she remains silent, it means that their nikaah is valid. So what is the correct opinion? Will the nikaah be valid or not if any one does like this? 

Q: My mom said that during marriage, the husbands family asks the girl if she had completed reading the Quran in front of an aalim/muallima/ustaadh.

I find no logic behind this, please tell the ruling about this according to the sunnah.

Q: Can a nikaah take place by responding yes to the words like "marry me" and "will you marry me"? What is the ruling of Islam in this matter?

Q: Can a woman perform nikaah of two people like nikaah molvi and nikaah qazi? This type of nikaah will be valid or not if performed by a woman qazi?

Q: Please let me know if there is any role of witnesses after the nikaah ceremony has been performed and they have signed the nikah document as witnesses?

Q: If a woman marries a man based on what he told her and later on she finds out that the man was untruthful, meaning he lied about everything just to get her to marry him. Is the nikaah invalid? Especially if he lied about being a practising Muslim which it turned out that he wasn't? Does she need to do iddat even if she only stayed with him for a week and she didn't engage in intercourse because she was on her period with this untruthful man?

Q: I’m married for 5 years and Masha Allah we live a happy life. And now my husband is asking permission from me for a second wife. But as of our life now I’m just thinking should I permit him for this or not because he has two big daughters of 15 years. He is unable to take care of them with some money problems. His mother is also living separate at his sister home but in need of all the childrens help. But my husband is unable to help her also. Now I’m also not living in a wealthy life with some money issues. So my question is in this case a second wife is permissible for him or not? Do I have to give permission or not?

Q: I am a Muslim Sunni Sayyed woman coming from a religious background. Recently a Christian man has approached me. He says he wants to marry me. I also like him. He is ready for doing nikaah. I am a follower of Islam and don't want to compromise on Islam. Kindly guide me if it is haram to marry a Christian or can I marry him. My religion is a priority for me.

Q: If a girl got pregnant before marriage and married another man without knowing that she is pregnant and when she found out about it after marriage that she is pregnant, is the nikaah done or not?

What is the relation of this child with her husband if the baby is a baby girl?