I am Prakash Shahi Thakuri and I tested the app of Teyi Tsai MinSDK: 19.
The code is available at: https://github.com/helentsai17/CS6392019/tree/master/FirebaseTraining
The minimum SDK is 19.
The target SDK is 29.
The code, the apk and a screenshot are not available in the GitHub repository.
The code does not uses fragments
It is connected to Firebase and all the dependencies are added.
I tested the app on Android Emulator Google Pixel XL
The app does not crash.