If you want some reliable free answers, why not email some lawyers directly. So far I know there are some lawyers who are happy to answer your legal questions without any charge. Such as:
http://www.fan-law.com/
http://www.mylawyerwang.com/
To people who want to answer legal questions, please only answer questions for which you are certain on the answers because of your own experince or research; For questions you do not have first-hand knowledge or some legal research, it is better for you to keep silent and let lawyers or people who CAN answer the questions to speak.
Good luck in your path toward GREEN CARD!