Managing a stage boundary can take place during a release review workshop as it involves reviewing the progress and planning for the next stage. This process looks both backwards to assess what has been achieved and forwards to plan future activities, making it integral to the release review. This allows the team to evaluate performance, quality, and benefits, and to ensure alignment with project goals moving forward.
The best description for the senior user role when tailoring the organization theme is an 'executive sponsor'. The senior user represents the interests of those who will use the project's products and is responsible for ensuring that the project's outcomes meet the needs and requirements of the organization. This is consistent with the role of an executive sponsor, who provides high-level support and ensures alignment with organizational objectives.