With a season pass, can you download dlcs that already came out

Found the answer,The code for the game is also the code for the DLC's.

In single player, go to the extras, then to redeem code, and enter the key for the game.

There are plenty of things you might not get if you played it without having an idea of the prequels. However, I wouldn't necessarily recommend playing them to get the story.

The first one is incredibly repetitive and involves many menial tasks whilst the second one struggles in aspects of the story line.

Strictly speaking, there won't necessarily be things you won't get, just things you won't notice. Most games are developed so that you would be able to understand the plot without having to play previous games (although I think most people would struggle with Metal Gear Solid 4).

I'd recommend either reading the wikis for the plots or there is a handy video here that will sum up everything brilliantly. (Obviously, don't watch if you wish to play the games instead)