Is firebase firestore safe?

Question

Hello. I want to use a firestore database for a code of mine, but I have some doubts.
1. Is it safe to publish the code? How do I prevent people editing my code to send infinite entries to the database?
2. If so, how can I make it safe so that only a certain amount of entries are allowed per user?
3. Is there something like JavaScript for Firestore? Like, I imagined it would be something like SELECT a FROM b, but it is more complicated than I thought.

Answer 1

I guess you are looking for security rules:
https://firebase.google.com/docs/rules?hl=en