When a project experiences a delay that could impact the schedule, the project manager should capture the risk in the risk register. This allows for the documentation of the risk and its potential impact, as well as the planning of appropriate response actions to mitigate the risk. The risk register is a key tool for risk management in projects, as it provides a structured way to track and monitor risks throughout the project lifecycle. By capturing the risk, the project manager can work on preventing the risk from becoming an issue, which aligns with the proactive approach to risk management advocated by PMI.
: (Project Management Institute. (2021). A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition and Standards. Project Management Institute.)

In an uncertain environment, it's crucial for a project manager to validate assumptions and assess risks. This involves identifying, evaluating, and controlling uncertain factors that can significantly affect the project's performance1. This process, known as risk management, helps to avoid or mitigate potential negative effects1. It's also important for the project manager to be comfortable with uncertainty and to be able to react to it in an agile, but well-structured way2. This approach gives the project team confidence that the project is still taking the right steps to deliver as planned2. References: 1 Managing Project Uncertainty: From Variation to Chaos, 2 Managing projects in uncertain times - APM

Effective communication is crucial for the success of virtual teams. Regularly collecting feedback from team members can help the project manager understand the effectiveness of current communication methods and identify areas for improvement. This approach aligns with PMI's emphasis on continuous engagement and iterative improvement in project management processes.
: The answer is supported by PMI's resources on best practices for managing and developing virtual project teams, which suggest that understanding team dynamics and maintaining open lines of communication are essential for virtual team engagement and performance12.

In projects with high levels of uncertainty, especially those that are innovative in nature, it is beneficial to increase the number of iterations. This allows for more frequent reassessments and adjustments, which can help in managing change requests more effectively. By breaking down the project into smaller parts and reassessing at the end of each iteration, the project manager can incorporate necessary changes in a controlled manner, thus reducing the overall number of change requests.
: The PMBOK Guide outlines the iterative approach as a means to manage and control projects with high uncertainty1. It suggests that iterative cycles allow for continuous improvement and adaptation, which is crucial for innovation projects2. The Professional in Business Analysis materials also support this approach, emphasizing the importance of iterative review and adaptation in response to change34.

In project management, particularly when tracking project benefits, it is essential to have well-defined KPIs to measure performance effectively. If KPIs are not yet defined, the project manager should collaborate with the benefit owner, who has a vested interest in the project's success. Together, they can identify the missing data, define the KPIs, and determine the best approach to track and report the KPIs. This collaborative effort ensures that the KPIs are aligned with the project's objectives and the benefit owner's expectations1.
References:
"30 Important Project Management KPIs (& How To Track Them)" from ClearPoint Strategy2.
"14 Project Management Metrics & KPIs You Need to Track" from FounderJar3.
Discussion on ExamTopics regarding project management and KPIs1.