Re: Is this typical 4 year-old behavior?
After my divorce, my daughter (3 at the time) and I moved in with my parents. My parents spoiled her rotten (as most grandparents tend to do). Her father was no longer a part of her life so my parents took on a very active role trying to fill in as the "other parent". We moved out when I remarried and we had a VERY hard time with her. She would tell us she wanted to live with Nana and Papa again and that they let her have her way. It was awful.
It took a while, I'm talking a few months, but with consistency her behavior improved. She got toys taken away when she did something unacceptable. She stood in the corner for telling me no. For every bad behavior or action she had we had a consiquence and we didn't let it slide once. Children need consistency when it comes to disapline, structure, and boundaries.
Your son is going through a confusing time. It sounds like there has been a lot a disruption to his daily routine and that can be very stressful for a child. Most adults have a hard time handling change. Make sure that you can provide him a schedule so he knows what to expect and make sure he knows what mom and dad consider unacceptable behavior. He won't like it at first. He will probably be even worse in the beginning. But if you stick to your guns it will get better.