Change management is important in a project because it provides structured processes and management products to manage and implement changes effectively. This ensures that all changes are assessed, approved, managed, and documented properly, helping the project adapt to changes while maintaining control and alignment with project objectives. References: PRINCE2 Foundation official resources and training on change management.

The Plans theme in PRINCE2 estimates the cost of delivering the project. This theme involves the preparation and maintenance of the necessary schedules and budgets to control the project, including outlining how, when, and by whom the project's products will be delivered and at what cost.
PRINCE2 7 Foundation handbook and documents.

The purposes of the quality theme in PRINCE2 are to establish how the project will ensure that products are fit for purpose and meet stakeholder expectations (purpose 2) and to ensure that the project's objectives are desirable and achievable, which pertains to ensuring that the project has a solid business justification (purpose
3). References: PRINCE2 Foundation Handbook, Quality Theme section.

The purpose of the Risk theme in PRINCE2 is to establish a cost-effective procedure to identify, assess, and control uncertainties or risks. This ensures that the project can cope with risks effectively. The Risk theme supports decision-making by improving the understanding of risks and their likely impact on achieving the project's objectives.
PRINCE2 7 Foundation resources and study materials.

The advantages of having a clear end to a project include ensuring that no further costs are incurred by the project (1) and that project products are transferred to operations and support for ongoing use (2). The achievement of all benefits at project closure (3) is not guaranteed and typically occurs post-project, and the project brief is not re-baselined at project end (4). References: PRINCE2 Foundation Handbook, Closing a Project section.