J.G.
This is all perfectly normal developmentally. Kids act up starting at the half year, leading to their bday. I have a 3.75 year old at my house, that was the sweetest, most cooperative sweetheart in the world. He is now yelling, barking orders and being generally unpleasant.
I find asking him to try again works. I also ask him if tantrums have worked in the past, and he usually stops and finds a nice voice. As I see it, my role is to help him pull himself together when the world isn't doing what he wants. Its also my job to give him lots of choices so he feels empowered. My little guy is now in charge of collecting garbage from the bedrooms and bringing the cans to the kitchen. He loves it. He also is learning to use the vacuum. Again, he loves it. He loves stripping his bed and helping wash his sheets, etc.
When he talks to you in ways you don't like, ask for a nice voice or ignore. He will quickly find his normal voice. With that said, there is something serious developmentally going on, so lots of cuddles and loving smiles, and lots of activities that make him feel empowered. And lots and lots of choices. Prevent power struggles, as that is what he is looking for to feel empowered.