Masaail pertaining to the Wali and Compatibility between spouses

Q: My daughter wants to get married to someone and she already has feelings for the boy. 

1. Can we as parents make Istikhara for her as we feel the boy is not compatible for her. 

2. If we do feel he is not compatible for her, what can we read for Allah Ta'alah to guide her and forget about this boy.

Q: 

1. What kind of illnesses would one have to disclose when seeking a wife? 

2. If the illness is not current, does it have to be disclosed i.e. if one used to have ocd/waswasa issues in the past and one has healed a great amount, would one have to inform a potential spouse of it in case it could creep up again? 

Q: Is marriage of a Sunni (Deobandi) girl valid to a Shia boy?

Q: I love a girl and she is a Wahabi girl and I am Ahl e Sunnat. Is it permissible in Islam for me to marry her?

Q: I am a 17 year old high school student, and really embarassed to ask such a question, so I seek Allah's forgiveness.

Since few months I have developed feelings for a celebrity girl who is in my age group. Though the intentions are not ill but I really want to marry her and oftenly ask Allah to make me marry her.

Is this type of dua ok and what should I do about it? Can you please guide me as per Islam.

Q: I am about to turn 19 and live in Canada. I am baligh since the age of 9 (which means I had my periods). I am currently in college and I like a guy. I want to do nikkah but my parents don't allow nikkah at such a young age specially till I don't complete my studies which has around 5 to 7 years.

I am scared of doing something haram (like zina) and I want to turn it halal as soon as possible. I have the witnesses, I am completely sure about this marriage since the guy belongs to a good family which is also religious and fulfils its Islamic duties. But I recently heard that nikkah without the consent of wali is invalid.

Now my question is, in what Hadith or verse of the Quran is it mentioned that the father should be wali? Can I make an imam my wali? Or can I conduct my nikkah without a wali while fulfilling other conditions such as witnesses, and haq mehar.

A detailed response over this matter for better insight would be appreciated. 

Q: Can a Muslim man make nikah with a second wife who is a Christian woman and then go to the church and watch her being baptised. Is this kind of marriage valid and accepted in Islam?

Q: I want to marry a woman who has become Muslim, but her family is kafir. Her father is divorced from her mother and has not lived with him for more than 10 years and she lives with her mother and younger brother.

In this case does the girl need to ask permission or have the consent of someone from her family (Wali) or can she marry me only with her own consent?

Q:

1. My husband married a Christiam girl who didn't convert to Islam. Is the nikaah valid?

2. He stays 1 night only with us and its affecting my children now. Is this permissible? He treats me, as a first wife, very badly. He talks rudely to me and is always angry with me. His 2nd family is always treated well.