how can you tell when you out of 4 wheel drive plus do both rear wheels spin when you are in or out of it

 

If you can spin the rear wheels, you are out of 4x4. If you have a locking rear diff, you will spin both rear tires.

A good way to tell if you are out of 4x4 is to turn on a dry road surface. The front of your truck will hop if you are locked in yet.

Also, the light in the dash will tell you.