Hello,
you're using simple questions, but an answer to those questions is rather complex and it's going to very much vary from company to company. See...
Company A) Harry & Greg Games
Harry just managed to finish writing a piece of code which allows for 10 000 AI actors to navigate without slowing the game to a crawl.
Harry: "Yo, Greg, I did the thing with the AI. Pull the newest version of the code an run those insane prototypes of yours against it, see if it all works properly."
Greg: "Thank you, Harry, you're brilliant!"
Company B) Awesome Games Incorporated
The AI department manager has received an e-mail that the ticket for allowing up to 10 000 AI actors to function simultaneously has just been marked as resolved by Pawn Coder 156, his code reviewed by Senior Pawn 5. He therefore passes the ticket on to his superior, who will give it to QA to see if previously unsatisfactory tests run properly now.
Company A) Harry & Greg Games
Harry: "Yo, I uploaded more awesome code to git!"
Greg: "And I uploaded the assets we talked about to google drive!"
*And there was much rejoicing*
Company B) Awesome Games Incorporated
The networking department manager gives a satisfied smile as he sees all the work hosted on company's private servers. The solid company's back-up policy gives him the assurance he needs to know that the licensed work will keep on making money for the years to come. The rack holding a git server winks at him merrily.
Company A) Harry & Greg Games
Greg: "Yo, harry, your engine's broken, can you fix it?"
Harry: "God damnit Greg, why do I do ALL the programming around here!?"
Greg: "I'm an artist man, I don't even know how to write letters!"
Company B) Awesome Games Incorporated
Manager Sally: "Hello, Martin. Could we borrow Senior Pawn 7? I hear he has a lot of experience in C++ optimization and we could use some tweaks to our engine, the C++ programmers who have the task assigned can't figure anything out anymore so we need a fresh outlook."
Manager Martin: "Of course, Sally. Would you be so kind as to fill out the Senior Pawn Leasing Form and run it past accounting so that his work is all in order?"
None. Start learning, start coding, see where it takes you. Don't worry about organizational structure until you actually start having an organization to be structured.
And if your organization starts having more than a few people and you notice issues with organizing, you may either approach someone who has experience leading larger organizations in general or - just start learning.
There are management schools and courses, both around you (probably) and online. Because when you are at a point of having people to manage, there are no easy answers you could simply find on discussion boards.
Edit:
Incidentally, do start by creating a simple game like space invaders from start to finish, intro to end credits. Don't skimp on anything - do your menu, do your leaderboards (bonus points if they're hosted online), create your settings menu with resolution options and rebindable keys, make the credits roll and appropriate music play while they do so. Draw your invaders and your tanks, get them into the game and manipulate them through the game world. Make the appropriate sounds play at the appropriate times.
When you get stuck and don't know how to solve an issue, do partake in online development communities like Unity forums or Game Development Stack Exchange. Communicate. Search. Learn.
When you successfully finish all of these things and your space invaders game does everything one would expect it to do, you'll suddenly understand how all the pieces fit together so much better than any amount of words could explain.