Chris
Alright, I'll take the bullet here.
An optimistic answer to the first question will be FOUR. The answer nowadays pivot around an average of five years (it is the answer I gave the HR anyways) Upon promotion, a Second Officer [ / ] will be promoted to Junior First Officer [// ], or what local pilots call 二柴, not three strips just yet. By the time a cadet become a fully recognized First Officer [///] it may take anywhere between 7 - 9 years.
In CX, upon completion of cadetship, cadets will move on to become SOs in the cockpits of Long Haul and Ultra Long haul flights. In regards to other airlines, SOs serve the function of the flight engineer AND relief pilot.
So the answer to your second question is YES and kind of... The term flight engineer is slowly disappearing because historically speaking not ALL flight engineers are pilots. On most airlines today, the position once know as flight engineers are occupied by relief pilots, and in the situation of CX, they are called Second Officers.
Ever heard of navigators?