- This validates the purpose of the B2 visa. If the officer ever found out your intention, they will not let you in for sure. If you don't have a VISA yet, I think K1 will be your best choice as K1 is the regular path for your case.
- Whether if it was allowed to change from B2 to green card. It was allowed, you would need to file I-130 and I-485 form. You can get those forms at
http://www.uscis.gov. Did you see I use the word "was". I was transferred from F1 status to Green card. However, the details of US immigration law changes from time to time. I think most of us never paid too much attention after we are done with our own application. I applied before 911 too, and there was a law call 245i, under this law, people can wait to change status even my original status was expired. The law was about to expired when I applied. But I don't know if the government ever renew it. So, you bf may be better to consult with an immigration lawyer to ensure the latest status, and question about the best way for you two.
- In my case, the officer did not ask any question. I was applied some days before 911. The case process was delayed for so long that time. When I went to interview for GC, my son was already 1 years old. With his birth certification, I guess my officer can be sure about my marriage.
- The dis-adv for going with B2 is that you cannot leave USA or you won't be able to enter again. The process time for GC should not be over 1 year for within USA, but US government can delay the apps from time to time.