EBS volumes provide block storage for EC2. A volume is placed in an Availability Zone and normally attaches to a compatible instance in that zone. An EBS snapshot is a recovery source from which you can create a volume; it isn't an extra live attachment. Keep those resource types separate when planning a restore.
Persistence also depends on configuration. A root volume can be configured to delete on termination, while instance-store data has its own host-related lifetime. Neither an attached disk nor a snapshot automatically proves application-consistent recovery. Coordinate application writes when necessary, record the recovery point, and test restoration. The edge case here is location: choosing a volume identifier alone doesn't establish that it can attach to the target instance's zone.