Various masaail of Nikaah

Q: This is my friends problem:

I am engaged to a girl. Last week I saw her with her uncle (aunts husband) involved in sex and I also found that she has an affair with 2 other people. My family and the girls family don't know about her illegal relations. Right now I am still engaged to her. Tell me what to do? I can not break the engagement because her family is very powerful. They have money and position. I cannot tell this to anyone because it is difficult for anyone to believe. I don't have proof except that I saw them with my own eyes. Please guide me what to do. Should I marry her or tell me any dua or wazifa which will help me to expose there sin in front of every one. I can't refuse this marriage or run way. 

Q: Is it advisable for one who has the need to get married to delay on account of studying further?

Q: A Muslim student studying in non muslim country since 2006.The home country & the place where parents are staying is not comfortable/stable and full of problems economically,socially,safety & politically. This country had very relaxed laws to work & stay in country after study in 2006 while student moved and had plan to take permanent residence which have been changed now in 2010 .The student plan to make court marriage with a Christian girl who want to help the student to stay in the country & get Green card /temporary residence and later permanent residence. This girl will get compensation from the student. This will be a paper marriage only to stay in the country after the education and later get residence. 

The student will not physically meet the girl but will relieve her after receiving the residence in the country.

The student will marry a muslim girl as his partner and use the foreign residence for his work & livelihood in muslim countries like Gulf states where he may benefit of foreign residence.

Q: What status does nikaah hold in Islam?

Q: Question is it my cousin he is missing from 10 year 7year to go he did not contact with wife according to one has kno wn person in Australis he say i will never contact with my family but problem is it has wife wanted to merry with me because she have 2 kids and very Alon and she much love me what we can do?

Q: Is it permissible for women to remain alone in their homes in order to allow their husbands to go out in the path of Allah (jamaat) or on business trips, etc. Please explain the correct Shar'iee ruling?