Yes they can. It is called phantom pregnancy and that is where the dog's body acts as though it is pregnant but really is not. You should see a vet to be absolutely sure your dog is not pregnant, but it is possible.
Yes, they can have false pregnancies and can even be stimulated by a baby animal. Dogs have been known to produce milk for another dogs babys, even other species.
Yes if they are having a false pregnancy
No， female dogs can not get milk in their boobs and not be pregnant.
If the dog didn't pregnant his chest wouldn't have milk.
No ,they can not.
I don't know my dog does that to. It lays down and milks but shes not pregnant.