API Billing - Subscription with free time

I’m creating a public application and when trying to implement the billing API according to the documentation, I realized that the documentation doesn’t have all the necessary information. Let’s get to the points:

What happens when I create a subscription with free usage time and then the following happens: this time ends, the customer pays the first invoice, uninstalls the app, and installs it again?

What happens if the customer installs the app and uninstalls it before the free time is up and installs it again?

Regarding the API, what would be the endpoint to query this free time that the customer used?