I have no problem with full motility of the neck after a facelift. Nevertheless you should solicit the instructions from your own surgeon.
After a face lift, you should be able to do range of motion type of movement on your neck, starting the next day. Actually, I strongly recommend my patients do that because if they keep the neck in a certain position, they may develop some scar bands, which may interfere with the result. For that reason, starting range of motion exercising the next day after surgery is a good idea.