http://chroniclesofelyria.gamepedia.com/Development_Timeline

That link should clear up that information.

i think the best thing to read is this KickStarter update called Kingdoms, Chornicles and Mud. Which describes each of the systems.

It is likely that prologue will go through the various access phases, so given to alpha backers first. However, if the other stages will too is uncertain. Though with KoE being part of land selection that is very likely to follow the order of people's influence.

KoE will effect your heritage. You are not playing as your current character but their ancestors. This means you might inherit a better starting County etc. Based on your actions but not skills or other character specific attributes.

Exposition carries over in full. It is a three month head start that allows the world to be built. It allows Kings to get into their Kingdoms and get settled before adding Dukes, then Counts etc. It also allows the ramping up of PvP which will start of very limited. Basically it is the build up so when launch comes CoE is a living, breathing world.