CloudFormation describes resources as a stack. A template uses logical identifiers, resource types, and properties; the deployed account contains physical resources. Updating a template is a controlled change to that stack, not merely saving a text document. References and dependencies help establish resource relationships.
A failed creation or update produces events that identify the failing resource and reason. Default rollback behavior aims to return the stack toward a prior controlled state; it doesn't justify ignoring data-retention requirements. Read events before repeatedly launching the same broken template. This simulator supports the documented local template subset, with JSON or YAML files and visible stack events. Unsupported resource types fail visibly rather than pretending a complete cloud deployment happened.