A benefits management plan is a document that describes how and when the benefits of the project will be delivered, and how they will be measured and evaluated. It also aligns the benefits with the organization's strategic objectives and shows how the project contributes to them. A benefits management plan can help the project manager communicate the value and benefits of the project to the stakeholders, especially if the project is in danger of failing or losing support. A benefits management plan is an output of the Identify Stakeholders process in the PMBOK Guide, and it is also covered in the PMI-PBA Exam Content Outline under Domain II: Needs Assessment. References:
PMBOK Guide, 7th edition, page 133
PMI-PBA Exam Content Outline, 2018, page 9

When concerns about meeting quality standards arise, it is crucial for the project manager to review the quality management plan with the senior manager. This allows both parties to understand the quality objectives, standards, and procedures that are in place, and to ensure that these align with the project's goals. The PMBOK Guide and best practices in project management emphasize the importance of regular quality assessments and the use of quality audits to ensure that project activities comply with the defined quality standards12. By reviewing the quality management plan, the project manager and senior manager can collaboratively address any gaps or misunderstandings and take necessary actions to meet the quality requirements.
References: =
PMI. (2002). Ensuring a quality project through the project review. Project Management Institute1.
Montgomery, J. D. (2000). Quality assessment and improvement processes and techniques. Project Management Institute2.

According to the PMP Exam Content Outline, one of the tasks of the project manager is to "Assess and prioritize impact on project scope, schedule, cost, quality, and risks of approved changes, and determine cause and effect relationships" (Task 5, Domain II: Process). This implies that the project manager should evaluate the impact of any change that affects the project performance, such as the removal of a key team member. By doing so, the project manager can identify the potential consequences and benefits of the change, and look for alternatives to mitigate the negative effects or enhance the positive ones. The project manager should also submit a change request if required, to update the project management plan and baselines accordingly. This will help to maintain the project alignment with the objectives and expectations of the stakeholders. References:
PMP Exam Content Outline, Domain II: Process, Task 5, page 101
PBA Exam Content Outline, Domain IV: Evaluation, Task 4, page 152
A Guide to the Project Management Body of Knowledge (PMBOK Guide), Sixth Edition, Chapter 4: Project Integration Management, Section 4.6: Perform Integrated Change Control, page 1233 Business Analysis for Practitioners: A Practice Guide, Chapter 6: Traceability and Monitoring, Section 6.4:
Manage Changes to Requirements, page 117

In a situation where a team member is struggling with a new system that was recently implemented, the project manager should assign an experienced resource to support the team member12. This approach ensures that the team member gets the necessary help to understand and adapt to the new system, thereby improving their performance and reducing the risk of project delay12. It's important to note that the project manager should approach the conversation respectfully and privately, focusing on the behavior and not the person2.
References: = How Project Managers Can Deal With Difficult Team Members, 7 Steps for Dealing with a Difficult Team Member - Project Bliss

According to the PMBOK Guide, an agile approach is suitable for projects that have a high degree of uncertainty and change, as it allows for frequent feedback, adaptation, and value delivery. An agile approach also enables the project team to demonstrate the benefits of the product to the sponsor and stakeholders through working increments or prototypes. Developing requirements and designs to support a faster product release may not address the uncertainty and change aspects of the project, and may compromise quality or scope. Emphasizing the adoption of a predictive approach may not be feasible or effective for a project that has a high degree of uncertainty and change, as it requires a detailed upfront planning and a rigid control of changes. Outsourcing development of the product to a third party may not be the best option for the project sponsor, who wants to see the benefits of the product demonstrated, and may introduce additional risks and challenges for the project management. References: PMBOK Guide, 7th Edition, Section 2.1.2, Agile Approach; Section 2.1.3, Hybrid Approach.