Can I sleep in my car over night, for one night during long car ride?

Yeah you can. I do it off an on on my trips every month. When you get tired, you get tired&it's better than getting into a wreck

You can sleep in your car as many nights as you want.

They have parking spaces for cars..

If you're DRIVING I wouldn't sleep during the trip, instead just pull off the road. And don't take a truck parking space

I've seen travel trailers park there

Yes