Explanation
Short Explanation: Scrum is a framework for delivering value to customers and stakeholders in an iterative and incremental way. Scrum does not prescribe how project budgeting and financial forecasting should be performed, but it does provide some principles and practices that can help with this process.
One of these principles is that each Sprint should produce a potentially releasable product Increment that delivers value and meets the Definition of Done. This means that several Sprints may be funded as a single release, with the result of each Sprint being releasable product12. This allows the Product Owner to decide when to release the product based on the feedback from the customers and stakeholders, and the market conditions.
Another principle is that Scrum promotes transparency, inspection, and adaptation. This means that the budgeting and forecasting process should be revisited as frequently as each Sprint to ensure value is being delivered for the investment spent13. This allows the Scrum Team to inspect the outcomes of the delivered Sprint Increments, compare them with the expected benefits and costs, and adapt the product backlog and the release plan accordingly.
Scrum does not align with traditional accounting practices that require fixed scope, cost, and time. However, this does not mean that Scrum Teams do not need a budgeting process or that they only need to cover the run cost (time and materials) of the Scrum Teams. Scrum Teams still need to estimate the size and value of the product backlog items, forecast the delivery date and cost of the product or release, and track the actual spending and revenue of the product or release43. The difference is that these estimates and forecasts are based on empirical data from previous Sprints, rather than on upfront assumptions or guesses. They are also subject to change as new information emerges or new requirements arise.
References:
Scrum Guide 2020, section "The Sprint", "The Increment", "Empiricism".
Tips for Effective Agile Budgeting and Forecasting | Toptal, section "Establish Context and Set Expectations", "Budget for Value".
Project forecasts and budgets | Microsoft Learn, section "Project forecasting".
Planning and Budgeting in Scrum Projects - PMHut, section "Budgeting in Scrum Projects".

The Scrum Master should do this because it is the most effective way to ensure that the Scrum Teams are self-organizing, cross-functional, and collaborative. The Scrum Master can help the Scrum Teams to understand the benefits of working together as one integrated team, rather than as separate component teams. The Scrum Master can also facilitate the communication and coordination among the Scrum Teams, and support them in resolving any dependencies or conflicts that may arise.

Explanation
A: Having one Product Owner will improve the clarity of accountability to the teams and to the product management department. This is a good suggestion, as it ensures that there is a single person who is responsible for maximizing the value of the product and managing the Product Backlog. Having one Product Owner also avoids confusion, duplication, or conflict among multiple Product Owners who may have different visions, priorities, or expectations for the product.
D: A single Product Backlog should be maintained holding all requirements for the new product. This is also a good suggestion, as it ensures that there is a single source of truth for the product requirements and that they are transparent and visible to all stakeholders. Having a single Product Backlog also enables the Product Owner to order the items based on their value, risk, dependency, and urgency, and to collaborate with the Scrum Teams to select and refine the items for each Sprint.
References:
The Scrum Guide, section 2.3 (The Scrum Team), page 7
The Scrum Guide, section 4.1 (The Product Backlog), page 11
The Scrum Master Learning Path, module 2 (The Scrum Framework), lesson 4 (Sprint Planning) and lesson 5 (The Sprint Review)

It is best to coach the Development Team members to collaborate on issues regardless of severity. They may consult the Scrum Master of Product Owner if needed.

Non-functional requirements should be worked on alongside functional development.