Question

This is a very dumb question, I’m sure. But is it possible for another app to overwrite your database if they used the exact database name?

Answer 1

No. Your app is in the sandbox that other apps can not access. At least on non-jailbroken device.

iOS Programming Guide

The Application Sandbox

For security reasons, iOS restricts each application (including its
preferences and data) to a unique location in the file system. This
restriction is part of the security feature known as the application’s
sandbox. The sandbox is a set of fine-grained controls limiting an
application’s access to files, preferences, network resources,
hardware, and so on. Each application has access to the contents of
its own sandbox but cannot access other applications’ sandboxes.