The 'Directing a Project' process in PRINCE2 starts when the request to authorize a project is received. This request usually comes after the initial project setup has been reviewed and there is a need to formally authorize the project to begin detailed planning and execution. This is a crucial step in establishing the governance framework that will guide the project's overall direction.References: (PRINCE2 7 Foundation Handbook, AXELOS)

The primary reason to perform the risk practice within a PRINCE2 project is to identify and manage risks that could affect the project's objectives. Effective risk management ensures that potential threats and opportunities are adequately assessed and handled to minimize negative impacts and leverage positives, thereby safeguarding the project's success.
PRINCE2 7 Foundation materials on risk management practices.

The Initiation Stage Plan specifies how the project board should approve management products produced during the 'initiating a project' process. It sets out the plan for the initiation stage, detailing the management and control of this stage, including how deliverables are to be reviewed and approved.
PRINCE2 7 Foundation Source: PRINCE2 Foundation handbook and online resources