In phase 3, you setup your phone in a way to keep them empowered and safe for years to come. Now they are trying out new apps and learning how they handle the added responsibility.
Coming up next is a slow introduction to social media. To justify access to Instagram (or similar), they should have an interest or hobby they wish to pursue that is hard or impossible without access to a social media platform.
You have to be ready too! With added responsibilities, it's important that you stay engaged to help with the teaching moments.