1. 
you could say that growth is broken down into a few fundamental questions:
How do I increase the rate of acquisition i.e. get more signups?
What can I do to activate as many users as quickly as possible in their first ‘N’ days?
What are the levers for engagement and retention and how can I pull them?
How do I bring churned users back into the system to “resurrect” them from the dead?

What are some decisions taken by the “Growth team” at Facebook that helped Facebook reach 500 million users?

    you could say that growth is broken down into a few fundamental questions:

    1. How do I increase the rate of acquisition i.e. get more signups?
    2. What can I do to activate as many users as quickly as possible in their first ‘N’ days?
    3. What are the levers for engagement and retention and how can I pull them?
    4. How do I bring churned users back into the system to “resurrect” them from the dead?

    What are some decisions taken by the “Growth team” at Facebook that helped Facebook reach 500 million users?