Is Google push notifications free?

Cloud Firestore includes a no-cost tier to help you get started at no cost . After you exceed the usage and storage quotas for the no-cost tier, you’re charged for the database operations you perform, the data you store, and the network bandwidth you use.

Yes, it FREE . To start any android application , the firebase is free till you reach some threshold value.

Yes. The usage of Firebase Cloud Messaging is free .

As per the current documentation, the Cloud Messaging Service (FCM) is free with no limits .