Conditions for the validity of Nikaah

Q: Is the Nikaah between a Sunni girl and a Shia boy halaal or not? The mother of boy is Sunni and the father is Shia. The same with their grand parents. They lived happily without interfering with each others maslak. They ask to do the Sunni nikaah and every thing according to our maslak. Please guide me with proper reference. The family of boy is not staunch. They don't do matam but they do disrespect the Sahaba ikram.

Q:

1. A girl was forced to accept a boy for Nikah. She was threatened to be killed by her parents if she refused and thus she accepted verbally and in writing against her will. She was not happy about the boy. After the Nikah she was forced to go live with him. After some time living with him she is still not happy about him. Was the Nikah valid? If not, then was all the time that was spent together (seclusion, talking, touching, etc...) considered sinful on both the boy and the girl? What should the girl do in this situation now? Is it Wajib for her to separate from him? What should the boy do if he finds out now that the girl was forced into the Nikah against her will?
2. In another scenario the girl was not threatened to be killed, but instead she was pressured by her parents and other relatives and she thus accepted verbally and in writing under their pressure to make them happy. However she herself was not happy with the Nikah. After the Nikah she was pressured to go live with him. After some time living with him she is still not happy about him. Was the Nikah valid? If not, then was all the time that was spent together (seclusion, talking, touching, etc...) considered sinful on both the boy and the girl? What should the girl do in this situation now? Is it Wajib for her to separate from him? What should the boy do if he finds out now that the girl was pressured into the Nikah and she is not happy with him?
3. If in scenario 1 the girl becomes happy with the boy after living with him for some time is the original Nikah still valid? Do they have to re-do the Nikah?
4. If in scenario 2 the girl becomes happy with the boy after living with him for some time is the original Nikah still valid? Do they have to re-do the Nikah?

Q: A friend of mines had a question about marrying a person who is a shia and willing to follow and raise the children as Sunni:

My question is that I want to marry this girl but she is Shia, if the girl is willing to marry me, raise our family and follow the Sunni way as my parents want is it gunaah or forbidden to marry a Shia if they do not convert? Her parents would accept me as a Sunni they just would not want her to convert but she will follow the Sunni way and also raise our chidlren sunni. Please keep in mind we have not talked to our parents about this situation yet and please give me some guidance as I do not want to go against anyone's parents. The only thing we have done so far is complete the isthikara which came out good alhumdulillah.

I did Istikhara for 7 days:

Istikhara: first night dream: He saw in his dream he was taking a picture of the girl and his family together like a group photo.

On the fifth night he did istikhara he had a dream where he saw lots of trees and her in a white shalwr kameez coming to his house accompanied by her little brother.

1. Is it gunna or forbidden to marry a Shia if they do not convert?

2. Is their a conversion process from Shia to Sunni? What does a Shia person have to do to become Sunni?

Q:

1. If a proposal and acceptance take place between a man or woman so are they married. Is this valid or legal in shariah.

Once in a TV program I heard that if a Muslim man and woman accept their proposal and accept each other then they are married and nikah takes place even if no one is present in between them. He said that this is called Nikah Ijaab and Qabool. Ss this true?

2. I also heard that for nikah Ijaab and Qabool​ permission, wish or willing of a woman's father is necessary.

3. If a man and woman accept each other in the presence of her mother and her 14 years old brother, so in this case nikah takes place or not?

4. If a father of a woman wishes to marry her daughter with his sister son (Nephew) and both the girl and boy are fiancee and fiance and both the parents wish to marry them but both girl and boy accept each other saying nikah words in the absence of any witness and both parents are also not present at that time so in this case nikaah takes place or not?

Q: For a man to marry a second wife, does he need to ask permission to his first wife?

Q: In my area the Shariah is not applied to its extent. My question is regarding marriage. There are many so called Muslims getting married according to the customs of this area which is not in compliance wih Shariah. People roam freely to choose and meet there life partners instead of the Shariah compliant way. Will these marriages be cosidered as Legal according Shariah?

Q: Does Islam allow one to marry to non muslim or muslim girl just to seek visa settlement and make a deal with her and pay her for that. After getting the visa the matter is finished. The marriage is just in papers.

Q: My question is can I do marriage just in papers not actually with proper intentions nor physically. Also the female knows its just for papers not actual marriage. Its just to gain visa. I consulted with a lot of people most of them said if you are not betraying the person its fine Islam allows to make secure your future and for a better life. The example in my mind is about our prophet Ibrahim (Alayhis Salaam). He said his wife is his sister. Its just to obtain UK registrar office certificate and to put it in file but to make a strong case you have to do nikaah as well. This all is in papers. Only I and her know about this that this is just for visa.

Q: Is it permissible for a women to have a contract before marriage stipulating that the husband cannot take another wife for five years. If it is permissible and the husband agrees and violates the agreement by taking another wife, does the wife have grounds for a khula?

Q: Is it permissible for a woman to stipulate before marriage that the husband cannot take another wife for a certain amount of years? If the husband does take another wife, does it nullify the nikkah?