Project assurance personnel should support the project manager by providing an independent view on the progress and performance of the project, ensuring that it adheres to the project plan and meets its objectives without directly managing any of the project activities.References: = PRINCE2 7 Foundation handbook and online resources

A minimum requirement for applying the Change Theme in PRINCE2 is to record every issue that is raised in the issue register. This ensures that all potential and actual deviations from the plan are captured and managed appropriately, maintaining control over changes and supporting effective decision-making. References:
PRINCE27 Foundation Handbook and official training materials.

The project manager needs to ensure that operational teams are responsible for running the project outputs during the step 'Transition the project into the organizational ecosystem'. This step involves integrating the project outcomes into the regular functions of the organization, ensuring that operational teams are prepared and accountable for maintaining and managing the project's outputs post-project completion.
(PRINCE2 7 Foundation Handbook, AXELOS)

The 'Manage by Stages' principle in PRINCE2 allows the project board to control the project effectively by reviewing its viability at the end of each management stage. This review process provides regular control points where the continuation of the project is assessed based on its performance and continued business justification. References: PRINCE2 7 Foundation Handbook and official training materials.