Cognac comes from the county of "Cognac" in France. If it's made in somewhere else, then it is not Cognac at all.
It is being kept in oak barrels for many years where it will get better tasting and get's it red-brown color.
Years in the barrel:
2 - *****, VS, Sélection, de Luxe
4 - VSOP, VO, Réserve, Vieux
6 - Napoleon, XO, Extra, Royal, Imperial
If your cognac is 20 years old, it still might be XO for example. That is only the minimal requirement.
Cognac DOES NOT get better in the bottle any more, only the years in the oak barrel do matter.