The primary purpose of the Quality theme in PRINCE2 is to establish and maintain the processes and procedures that will ensure all products created during the project meet the predefined quality requirements.
This includes planning, assurance, and control of quality. The Quality theme focuses on defining and implementing quality standards that the project must adhere to, rather than dealing directly with broader organizational quality assurance or the project scope.References: PRINCE2 7 Foundation handbook and other official documents.

The 'defined roles and responsibilities' principle in PRINCE2 is essential because it ensures clarity and efficiency in project management. By clearly defining roles and responsibilities, everyone involved in the project understands their tasks, responsibilities, and reporting relationships. This clarity helps in reducing confusion and improving communication and accountability among project team members.References:
PRINCE2 Foundation Manual

During the Starting up a Project process, one of the key activities is to create role descriptions for the project management team. This ensures that everyone involved understands their responsibilities and the expectations placed upon them before the project commences. References: PRINCE2 Foundation Training Manual; PRINCE2 2017 Foundation handbook.

In PRINCE2, a project is defined as a temporary organization that is set up to deliver one or more business products according to an agreed Business Case. The temporary nature of projects highlights their finite and unique aspects, distinguishing them from regular, ongoing operations. References: PRINCE2 Foundation manual, PRINCE2 official resources

The Issue Register in PRINCE2 is used to capture and record all issues that may affect the project but it is not designed to capture external events unless they become issues directly impacting project deliverables or processes. Its primary function is to log problems identified in project execution, not general external events.
References: PRINCE2 Foundation official study guide and online resources.