After a project was delivered, the business analyst learns of a project objective with no associated requirement. What would have helped determine this issue before delivery?

Which technique allows the collection of the maximum number of ideas on a subject from a group without considering the validity or practicality of the ideas?

A company is developing a new product for a customer and is required to verify and validate the product against the customer's acceptance test plan and requirements. The product was successfully verified against the acceptance test criteria, but the customer does not believe that the product meets the requirements.
This occurred because the customer's acceptance test plan:

During user acceptance testing, a defect is logged by a user from a department that did not participate in the requirements analysis. To avoid this situation and minimize impact on the project, the user should have been:

A company is in the final phases of implementing a project for a client. Which tool or technique could the business analyst use to iteratively validate the solution?