Hello - I recently picked up my first MacBook Pro, a 2012 model from a high school sale for $250. I installed 16gb ram and a 250gb SSD. So far so good. I have a question about iMessage. Does iMessage on the Macbook download all of my iMessages from my iPhone? Or does it only get messages from the point of activation? Currently I am running El Captain, any reason to upgrade to Sierra? Thanks!