Restoring data from previous snapshot on same instance:
If JIRA data (Testcase, version, project, component etc) changed since the snapshot is taken, this is likely to create orphaned references
Restoring data from previous snapshot from a another JIRA instance:
This data can’t be restored.
Restoring data from a another JIRA OnDemand instance:
This functionality is not supported.
Restoring data from previous snapshot with imported project:
Because imported JIRA data has different identifiers, restore process will result in bad or orphan references.