The Product Owner should not have the entire Product Backlog documented in detail before the first Sprint can start. This is because:
* The Product Backlog is an emergent, ordered list of what is needed to improve the product. It is never complete and constantly changes to reflect the needs and desires of the customers, users, and stakeholders.
* The Product Owner is accountable for maximizing the value of the product resulting from the work of the Scrum Team. They are responsible for identifying and articulating the Product Goal, which is a long-term objective for the product that guides all the activities of the Scrum Team.
* The Product Owner collaborates with the Developers and the stakeholders to refine the Product Backlog as needed to ensure that there are enough items that are sufficiently clear and ready for selection in Sprint Planning. The amount of detail and precision required for each Product Backlog item depends on its order, size, and complexity.
* The Product Owner does not need to have the entire Product Backlog documented in detail before the
* first Sprint can start, as this would imply a fixed and upfront plan that does not allow for feedback, learning, and adaptation. Instead, the Product Owner only needs to have enough items that are well understood and valuable for the Scrum Team to start working on them in the first Sprint.
References:
* [Scrum Guide], page 11, section "Product Backlog"
* [Scrum Guide], page 6, section "Product Owner"
* [Scrum Guide], page 10, section "Product Goal"
* [Scrum Guide], page 12, section "Product Backlog Refinement"

The metrics that will help a Product Owner determine if a product is delivering value are customer satisfaction and time to market. This is because:
* Customer satisfaction is a measure of how well the product meets the needs and expectations of the customers5. It reflects the value proposition of the product and the feedback from the users.
* Time to market is a measure of how quickly the product can be delivered to the market. It reflects the agility and responsiveness of the Scrum Team and the ability to deliver value early and often.
Other metrics, such as productivity, velocity, and percentage of scope implemented, are not directly related to value delivery. They may indicate how efficiently or effectively the Scrum Team is working, but they do not necessarily reflect how valuable or desirable the product is for the customers or stakeholders.
References:
Professional Scrum Product Owner™ Training, page 5, section "Product Value" Professional Scrum Product Owner™ Training, page 6, section "Product Vision" Professional Scrum Product Owner™ Training, page 7, section "Product Backlog Management" Professional Scrum Product Owner™ Training, page 8, section "Release Management" Professional Scrum Product Owner™ Training, page 9, section "Business Strategy" Professional Scrum Product Owner™ Training, page 10, section "Stakeholders and Customers"

Explanation
The Daily Scrum is an event for and by the Developers. They can choose whatever structure and technique they want, as long as they focus on the progress toward the Sprint Goal and produce an actionable plan for the next day of work12. The Scrum Master, the Product Owner, and the person coming in last are not necessarily the ones who should start the Daily Scrum. The person who has the token is a possible technique, but not the only one3.

Explanation
New work or further decomposition of work is added to the Sprint Backlog as soon as possible after it is identified because:
* It reflects the current state of the Sprint. The Sprint Backlog is a plan that the Developers create and update throughout the Sprint, based on their progress, learnings, and changes. By adding new work or further decomposition of work to the Sprint Backlog promptly, the Developers can ensure that the Sprint Backlog is transparent, accurate, and up-to-date.
* It enables the Developers to self-manage their work. The Developers are accountable for organizing and managing their own work, and they have the authority to change the Sprint Backlog as needed. By adding new work or further decomposition of work to the Sprint Backlog promptly, the Developers can exercise their autonomy and empowerment, and adjust their plan accordingly.
* It supports the achievement of the Sprint Goal. The Sprint Goal is a single objective that provides guidance and focus for the Developers throughout the Sprint. By adding new work or further decomposition of work to the Sprint Backlog promptly, the Developers can ensure that their work is aligned with and contributes to the Sprint Goal.
References:
* Scrum Guide 2020, page 6: "Developers are the people in the Scrum Team that are committed to creating any aspect of a usable Increment each Sprint."
* Scrum Guide 2020, page 6: "The Developers are accountable for ... organizing and managing their work."
* Scrum Guide 2020, page 10: "The Sprint Goal is a single objective for the Sprint."
* Scrum Guide 2020, page 14: "The purpose of each Sprint is to deliver Increments of potentially releasable functionality that adhere to the Scrum Team's current Definition of Done."
* Scrum Guide 2020, page 14: "The Sprint Backlog is composed of ... all of the work needed to deliver a product Increment that meets the Definition of Done."
* Scrum Guide 2020, page 14: "The Developers can change the content of the Sprint Backlog throughout the Sprint as more is learned."