Which document best provides the boundaries for product development?

The business managers had clearly slated that the delivered website must simultaneously accommodate millions of users around the globe. However, within the first week of the production launch, the website crashes frequently.
This situation could have been averted if:

Change control systems include provisions to implement changes without formal review in the event of an emergency. When this provision is utilized:

The business analyst is in the process of implementing a solution for a customer. The team is having difficulty confirming if certain requirements have been met. What could have caused this issue?

A project team has been assembled to reduce production costs. The business analyst is working with the project team to review and approve requirements. A stakeholder from the assembly line area has an issue with one of the requirements since it is dependent on using existing equipment that is set to be retired within the next six months.
Which of these techniques would the business analyst use to manage issues identified by stakeholders with requirements to ensure that those issues are resolved?