Do you mean by 3 stages the 3 classes?
Improvements are as follows, afaik
New seat which turns into completely flat bed, 201cm long, 60cm wide.
No big change at present, except DVD in MD11s.
Economy long haul:
Water bottle in seat pocket.
Amenity kit (incl. headphones to keep)
Better food, better presented + snack service in galley
NB The above is all I can remember off hand. Others might tell more or different.
And yes, I really work for SR. Why would you doubt me