Which database to choose for an iOS toy?

Question

Swift

In all the lessons they talk about firebase, but I doubt it a little, because I have never heard anything about this thing

Answer 1

If the state is only online then the choice is good, if you need only local then sqlite is better

Answer 2

What do you need to store? If something simple like last result, selected settings and something like that, then choose UserDefaults. If you need to record the fact of buying something inside the game, then use Keychain. If there is more data and you need a full-fledged database, then look towards CoreData or Realm. By the way, CoreData can store data in the cloud using CloudKit and it's free. But if you have a cross-platform, you need backing and all that, then take Firebase.
Here is a great article on the subject: https://fluffy.es/persist-data/