Trial application

Sorry i’m forgot mention if the device don’t have internet connection you need to config this for you app can’t read the Firebase Database Tag.
This Firebase Database guide by @Chirubot i’m shure help you to implement Firebase Database in your app

Edit

Don’t need to store any IP, serial number, IMEI or Login
The access to the app is for all user. Only use my suggestion and when trial period expired delete or change the Tag Value of Firebase Database.