The project manager should first revisit the project charter and assess if the project goals and objectives can be met with other alternatives. This could include re-evaluating the project requirements, researching other suppliers and/or re-designing the project in order to reduce the cost. If all other alternatives are exhausted, then the project manager should seek approval from the project sponsor or the CEO to proceed with the purchase order.

Ensuring compliance adherence is a continuous process that should be integrated into the project's development tools and practices. This proactive approach allows for ongoing monitoring and management of compliance requirements, which is essential in maintaining the integrity of the project and meeting mandatory guidelines. Including compliance within the development tools ensures that compliance checks are part of the daily workflow, making it easier to address potential issues as they arise and reducing the risk of non- compliance. This method aligns with the PMI's principles of integrating project compliance as part of the project management process123.
References:
PMI's Guide to the Project Management Body of Knowledge (PMBOK Guide)4
Planning and Managing Project Compliance (2021 Update)5
Plan and Manage Project Compliance - PM Illustrated PMP Exam2
How compliance in project management works | microTOOL3

The project manager should meet with the project team to assess their current skills and identify any gaps or training needs that may affect the project execution. This is part of the Plan Resource Management process, which involves determining the project roles, responsibilities, required skills, and reporting relationships1.
Sending the list to the project team and asking them to get training on the required skills (A) is not a proactive or effective way of managing the project resources. Asking the functional manager to review the resource pool and recommend the right individuals to join the team (B) is not feasible since the project team has already been assigned. Discussing the list with the project sponsor to confirm that the resources have the required skills is not the responsibility of the project sponsor, who is mainly concerned with the project benefits and alignment with the strategic objectives2. References:
* 1: A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Chapter 8, Section 8.1.3.1
* 2: A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Chapter 4, Section 4.1.2.1

The PMBOK Guide emphasizes the importance of team dynamics and conflict resolution. It suggests that project managers should foster an environment where team members can openly discuss and resolve conflicts.
This includes encouraging innovative ideas and addressing any concerns about their practicality. By promoting further discussions, the project manager can help the team integrate diverse perspectives and find realistic ways to implement innovative solutions12. References: = Conflict Resolution Strategies In Project Management (PMP)1; 5 Conflict Resolution Techniques in Project Management2.