Conditions for the validity of Nikaah

Q: I am a Muslim guy and I have been in a relationship with a christian girl for a while. I am trying to make this relationship permissible on all aspects and I want to marry her but we are not planning to register this marriage in the court (not legal marriage) just Islamic so that we can be confident that whatever we are doing is not a sin/Haram. We are very serious in this relationship and we want to take it to a legal marriage level but not now since she is still a college student and her parents and not fine with her getting married that early. I believe, I can fulfil all the Islamic marriage requirements from bringing in witnesses to announcing my marriage. It's worth mentioning that we live apart in two different cities, more than 6 hours away from each other but we do see each other every once in a while.

My question is: Is marry this girl according to the Islamic laws permissible?

Q: I'm in love with a girl who is 7 years older than me and she love me as much as I do. We both want to get married and start a life. So to ask her hand for marriage there is one thing I want to know, is it permissible to marry someone older than you like with 7 years age gap? And we both meet each other everyday as she is my teacher and I'm her student, she teaches me. So is it okay?

Q: During my nikah, I was not opposed to the marriage, however the witness only asked me who I wished to take as my representative, not if I accepted the marriage or not. My brother performed the qubool on my behalf. Is this correct, or did I have to verbally say I accepted the marriage?

Q: If a boy asks a girl in front of people *Do you want to marry me* or *Will you marry me* and the girl replies yes, does that mean they are married?

Q: Is civil marriage in a court accepted in Islam?

Q: Someone has told me that it is permissible to marry a Christian man, a Christian that doesn't convert to Islam and still have a halal marriage. This sounds totally incorrect and wrong, please elaborate.

Q: I am a Sunni Muslim and I had a question about a Sunni - Shia marriage. Am I violating my belief if I compromise with my shia wife to not name my child the names of the first three caliphs?

Q: About 10 years back I was in a boyfriend girlfriend relationship with a non Muslim boy and wanted to marry him. (Astaghfirullah) One day while we were talking over the phone, I got emotionally carried away and said qubul hai to him thrice like I had seen in the movies and series. That was it. There was no one else, no other thing or condition, I just spoke! Now was this a nikah?

I have sincerely repented for my mistakes and feelings for a non-Muslim boy from Allah Ta'ala and still repent daily for every wrong doing of mine! I would request you to. I am now married and a mother of one. 

Q: My muslim friend wants to get married to an atheist guy from thailand. My friend said that she will mary him after he converts to Islam. But the atheist guy said that he only will convert to Islam because he wants to marry her not because he believes in Islam. Is this marriage haram? Shall I try to stop my friend from marrying this atheist guy?

Q:

1. During nikah, does ijaab and qabool have to be said in the past tense?

2. If they are not said in the past tense, is the nikaah invalid?