whats the billing model for ebs snapshots?

You are charged based on the size of your snapshot and the length of time that you keep the snapshot. You are charged in terms of gigabyte-month.

Can you create EBS volume from an EBS snapshot?

Yes, You can create EBS volume from EBS snapshot. The volume created will be the exact replica of the volume from which the snapshot was created at that point of time.

which AWS service is used to manage snapshots of EBS volumes?

The snapshots that are created are saved in amazon s3 bucket.

which AWS service is used to manage snapshots of EBS volumes?

Can you create EBS volume from an EBS snapshot?