My I-140 and I-485 is pending, my OPT has expired. Can I stay back in the U.S until I get my green card EAD ?
Sure, because you have your I-485 pending. Having a pending I-485 gives you the right to stay in the United States.
Have any rules changed regarding getting a spouse visa through H1, L1, or O1? Also is traveling on a tourist visa to the US after marriage not ok, with a pending GC application? Finally, does the US have any special agreements with the UK, EU, Singapore, Dubai or Australia for visas that may qualify in this scenario?
Regarding the rules for getting a spouse visa through H-1 L-1 or O-1 nothing has changed.
It is certainly fine traveling with a tourist visa to the US after marriage, if you can convince the government that you are not going to break the laws which means staying in violation of your visa.
Regarding the US having any special agreements, there are only two kinds of visitor visas: regular ones and visa waiver or ESTA visa. There are special visas for example in Australia there is something called an E-3 visa which is very much like an H-1B and more or less a dual intent visa.
My and my wife's I-485 has been approved last week (PD 07/2005) without any RFE. I'd like to express my thanks to Rajiv Khanna's office for making my PR finally come true.