Not all whey protein powders are lactose free. Cheaper, less efficient whey protein powders are made with whey concentrate and contain high lactose levels.
Most whey isolates contain little or no lactose content due to the filtering process they undergo during manufacture.
Unfortunately no, whey concentrate tends to retain quite high lactose levels and is unsuitable for those with lactose intolerance.
Yes, whey hydrolysate is a highly refined whey protein that has been filtered of carbs, fats and lactose content.
Casein, also known as Micellar Casein is normally quite high in lactose and is not suitable for those with lactose intolerance.