I worked at Wal-Mart the year I graduated college. It was also the first year the store was converted to a Supercenter. Supercenters only close on Christmas (maybe Easter) unless there is a local/state law that says otherwise. The employees were all pissed because when it was a regular Wal-Mart they weren't open on Thanksgiving. Employees were told that all employees at the store would work Thanksgiving or Black Friday with no exceptions. I got a full-time job and quit before Thanksgiving.
As pp mentioned, they just bring the pallets to the floor shrink wrapped. Employees stand with the pallets until they are unwrapped at whatever time the store designates the sale starts. Also, the registers are programmed to not accept the sale price until the time of the sale.
As for cutting hours, that's nothing new. It was drilled into our heads that we were never to have overtime. If you were required to stay late one day to help with something or to clean the shelves in your area, you were required to come in that many minutes later the next day. There was a rumor that if you hit overtime that you had to meet with the store manager and the district manager to explain why. It was also said that your department manager would get written up if you had overtime. I don't know if any of that is true because no one ever went into OT while I was there.