How can GTA V be made in a week?

It can't.

It took five years to make GTA V and the work of over 1000 people.

There is no valid hypothesis for a way it could be done in a week.

No technology can replace the creative work of hundred of artists, animators, writers, designers, and audio engineers. No technology could ever facilitate the communication of all those people in such a short amount of time.

You couldn't even record the nearly 160,000 lines of dialogue in a week.

That you are even asking show only that you don't actually know anything about the real work that goes into developing a product.