Can a first Sprint start without a complete and exhaustive Product Backlog?

In Scrum, a first Sprint can indeed start without a complete and exhaustive Product Backlog. The essence of Scrum lies in its iterative and incremental approach to product development. The Product Backlog is a living artifact that evolves over time as more is learned about the product and its users.

Starting a Sprint with an incomplete Product Backlog allows the Scrum Team to begin delivering value right away and encourages collaboration and feedback. It's common for the backlog to be imperfect at the start, as the Product Owner continues to gather requirements and prioritize them based on stakeholder needs and feedback. This promotes agility, allowing teams to adapt and refine their approach as they better understand the scope of work and the needs of the users.

This approach aligns with the principles of Scrum, which emphasize the importance of learning and discovery throughout the development process. Moreover, starting with an initial backlog item or items enables teams to gain insights that can inform future backlog refinements and priorities.