A very NOOB question

It is required to read the entire documentation like programming guide even if i can understand code of projects like Tower Defence etc?
And which is the best way to learn UE4 API?
And programmers of AAA titles like Batman:Arkham Origins or Arkham Knight know the entire documentation or even more than that or they just start coding right away with API I mean like how they do this type of amazing stuff?
Actually I didnt slept whole night wondering about these things, so I couldnt stop myself!! and I am really sorry for posting these NOOB questions.

I guess I have to figure it out myself.

Actually, you don’t **have **to, you can. It will for sure help you. Reading teh documentation, reading the marketplace project examples, and what is the most important, just trying to code something. It’s not a short process, but in some time you will kow the whole documentation and more. No, you don’t need to read all classes of the engine, jsut lear the game framework first, nad check out the getting started tutorials.

Also, remember, you have to wait for an answer, it takes some time for someoen to read this.