An agile leader should ensure participation from all team members in the final phase of a complex project, as this will help to foster collaboration, communication, feedback, and alignment among the project stakeholders. Participation from all team members will also help to identify and resolve any integration issues, risks, or dependencies that may arise during the delivery stage. Participation from all team members will also promote a sense of ownership, accountability, and commitment to the project outcomes. Asking the client to attend all daily calls may not be feasible or necessary, as the client may have other priorities or constraints.
Ensuring cross-departmental teams are colocated may not be possible or beneficial, as the project may involve remote or distributed teams, or different organizational cultures. Requesting additional project resources may not be the best option, as it may introduce new challenges such as coordination, training, or integration costs. References: PMBOK Guide, 7th edition, pages 99, 100, 101, 102.

A statement of work (SOW) is a formal document that outlines the specific tasks, deliverables, and requirements of a project. It serves as a contractual agreement between a vendor and a client, providing a comprehensive description of the work to be performed. A SOW is used to document the project deliverables when outsourcing work to external parties, as it defines the scope, schedule, quality, and payment terms of the project. A SOW can also include a work breakdown structure (WBS), which is a hierarchical decomposition of the project deliverables into smaller, manageable components. References:
* What Is a Statement of Work (SOW)? - Coursera
* Statement Of Work Ultimate Guide: Simple Definition & Template
* What Is a Statement of Work? Definition & Examples - ProjectManager

In a situation where a contractor has not yet confirmed that they can meet the required schedule, the project manager should take proactive steps to manage the potential risk. This includes planning the task delivery with the contractor or vendor, and highlighting the criticality of the current situation1. This approach aligns with the principles of effective project management, which emphasize the importance of communication, risk management, and proactive problem-solving. References: NEC Contract

When a stakeholder demands the implementation of requirements that are out of scope without additional cost, the project manager should refer to the project's statement of work (SOW). The SOW is a formal document that defines the work activities, deliverables, and timeline a vendor will execute for a customer. It serves as a legally binding agreement that specifies what is included in the project scope and, by extension, what is not. If the stakeholder's demands are not included in the SOW, they are considered out of scope, and the project manager should clarify this to the stakeholder. Implementing out-of-scope requirements without adjusting the project's cost, time, and resources can lead to scope creep, which can jeopardize the project's success.
: The answer is verified with the principles found in the PMI's A Guide to the Project Management Body of Knowledge (PMBOK Guide) and the Professional in Business Analysis Reference Materials provided by PMI12345.

The project manager should refer to the requirements traceability matrix to verify whether the customer's claims are valid or not. The requirements traceability matrix is a grid that links product requirements from their origin to the deliverables that satisfy them1. It helps to ensure that each requirement adds business value by linking it to the business and project objectives2. It also provides a means to track requirements throughout the project life cycle, helping to ensure that requirements approved in the project scope statement are delivered at the end of the project3. Revising the project scope baseline (B) is not a good option since it would imply accepting the change requests without verifying their validity. Escalating the change request to the project sponsor is also not advisable since the project manager should first analyze the situation and propose a solution. Reviewing the approved project charter (D) is not relevant since the project charter does not contain the detailed product requirements. References:
* 1: A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Glossary, page 717
* 2: A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Chapter 5, Section 5.2.3.1
* 3: A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Chapter 5, Section 5.6.3.1