Film 'Inception'..the beginning... was it related to the ending?

i've just watched the film 'Inception' starring leonardo di caprio and i thoroughly enjoyed it.awesome premise and brilliant effects.but i just wanted to know whether the opening sequences with Cobbs on the beach then taken into Saito's palace where he's an old man ,whether it's related in any way to the same scene near the end? and what were the time differences between dreamworld and reality?plus how long did it take Cobbs to find Saito and why has Saito aged for they could only have been a few hours further in dreamland than the rest of the team as they were all eventually awake together onboard the same 10 hour flight from Sidney to LA.