Many people misinterpret the Scrum Guide as stating the Development Team size is limited to 3-9 members.
In reality, it only states that there is inherent risk attached to having less than 3 members and more than 9 members. As the number of members increases, the lines of communication also increase. This can be calculated using the Group intercommunication formula: n(n − 1) / 2 where n is the number of members.
Some teams are able to handle the risk and "synergize" whereas others might struggle. Saying that, the relationship between defining a Sprint Goal and Development Team size is unclear.
But the relationship between the ordering of the Product Backlog, the PO having clear objectives, and the Sprint Goal are direct. The Product Owner typically comes to the Sprint Planning with a business objective in mind and Product Backlog items related to the business objective. After deciding what can be done for the upcoming Sprint, the Scrum Team will craft a Sprint Goal that would be met through the implementation of the items. This is not dependent on the size of the team nor length of the Sprint.
Scrum is also a framework that's fit for purpose. Some projects/products are not fit for Scrum... or, better stated, Scrum is not suitable for all projects/products.

This is a good answer because it is consistent with the Scrum Master's accountability to serve the Scrum Team and the organization by identifying and addressing the factors that hinder the team's effectiveness. By informing management of the organizational impediments, you can leverage their authority and influence to resolve them. By enlisting their help, you can also foster a collaborative and supportive relationship with them.
This is another good answer because it is consistent with the Scrum Master's accountability to educate and coach the organization on the Scrum framework and its principles. By explaining how velocity is used in Scrum, you can help management understand that it is not a reliable metric for measuring performance or comparing teams. By referring management to the Product Owner, you can also respect the Product Owner's accountability to manage the product backlog and communicate the value and status of the product34.

Explanation
Coach the Product Owner that achieving the Sprint Goal is the Scrum Team's objective. A forecast is only used to initially estimate the effort required to reach the Sprint Goal.
This is true because the Scrum Master's role is to help the Product Owner understand the Scrum framework and its principles, such as empiricism, self-organization, and collaboration12. The Scrum Master should also remind the Product Owner that the forecast is not a commitment, but a plan that can be adjusted based on the Sprint progress and feedback3 . The Scrum Master should focus on the value and outcome of the Sprint, rather than the output and scope.
References: 1: What is a Scrum Master? | Scrum.org 2: What is a scrum master? [+ Responsibilities] | Atlassian 3: [Scrum Guide | Scrum Guides] : What Is a Scrum Master (and How Do I Become One)? - Coursera

This is a good way to challenge the decision and make them think about the consequences of lowering the quality standards. The Scrum Master can help them understand the importance of delivering a potentially releasable product increment that meets the expectations of the stakeholders and customers.
This is a good way to explore the root cause of the issue and find out why they are not able to complete regression testing for all of the selected Product Backlog items in the Sprint. The Scrum Master can help them identify and remove any impediments or inefficiencies that prevent them from achieving their Sprint Goal.

Explanation
The Scrum Value of openness can easily impact all of the aspects listed in the question. Openness means that the Scrum Team and the stakeholders agree to be transparent about their work, their challenges, their learnings, and their progress. This fosters a culture of collaboration, trust, feedback, and continuous improvement. Openness also helps to ensure that the product quality meets the expectations of the customers and the stakeholders, and that the product is delivered in a timely manner. Openness also contributes to employee satisfaction, as it allows the Scrum Team members to express their opinions, share their ideas, and learn from each other.
References:
The Scrum Guide, section 2.2 (Scrum Values), page 6
The Scrum Master Learning Path, module 1 (Scrum Theory), lesson 3 (Scrum Values)