Restore database in Firebase

If you delete your project, dont worry. You have 30 days for recovery in Google Cloud Platform. Then you will receive a email with a link for this.

https://console.developers.google.com/cloud-resource-manager?pendingDeletion=true&organizationId= some ID

Firebase keeps backups of the data in your Realtime Database. If you accidentally delete data from your database, you can reach out to Firebase support and ask for the data to be restored.

You can also check out Announcing Automated Daily Backups for the Firebase Database

I am sorry but the answer is no. the rollback is available only with firebase hosting.

for the future you should download a backup by simply clicking on 'Export Data' in your project root.