Some constitutional principles that might be applied to the issue of same-sex marriage are: the equal protection clause, the full-faith-and-credit clause, the separation of church and state and the freedom of religion. It is important to note that marriage is not explicitly mentioned in the US Constitution.
Same-sex marriage is constitutional because under the US Constitution, individual states have the right to pass their own marriage laws, including those legalizing same-sex marriage. Now, if your question is how is same-sex marriage MANDATED by the constitution, well ... it isn't, at least not explicitly. However, laws limiting marriage to heterosexual couples have been struck down by state supreme courts as unconstitutional. The final decision on interpreting the constitution on this issue rests with the US Supreme Court.
I don't think you can. You either has to be single or married to adopt. Just living together is neither. if you are in a samesex relationship and has gone through partnership might be possible though.
Anyone can do anything they want to as long as they truly want it. No, in Islam having a boyfriend/girlfriend type of relationship is not allowed whether your a male or a female and whether the bf/gf is Muslim or not. If you have anymore questions regarding the matter, just ask and I'll be happy to answer them. i gree in islam having a boyfrnd or a grlfrnd is not allowd but today no youngr generation follows it .....so if a muslim girl personlly like a non muslim boy...then it is not allowd in islam.....u cannot marry him unless he accpts islam...:)