The Sprint Goal is an objective set for the Sprint that can be met through the implementation of Product Backlog. It provides guidance to the Developers on why it is building the Increment. It is created during the Sprint Planning meeting.

There is no official rule that states that a Scrum Master cannot also be a Developer.

However, it is not best practice. So he can, but shouldn't.

A Sprint could be cancelled if the Sprint Goal becomes obsolete. This might occur if the company changes direction or if market or technology conditions change. In general, a Sprint should be cancelled if it no longer makes sense given the circumstances. But, due to the short duration of Sprints, cancellation rarely makes sense.

"The Scrum Team turns a selection of the work into an Increment of value during a Sprint."

The Scrum Guide (TM) of 2020.

In Scrum, the length of the Sprint Planning meeting can vary depending on the length of the Sprint and the complexity of the work that needs to be planned. However, the general guideline is that the Sprint Planning meeting should be no more than 8 hours for a one-month Sprint.

Note: There is no need to decompose all the Items in the Sprint Backlog. It can be done only for the first days of the Sprint.

The Scrum Master is a true leader who can coach the Scrum Team when needed.

The Sprint Goal is the single objective for the Sprint. Although the Sprint Goal is a commitment by the Developers, it provides flexibility in terms of the exact work needed to achieve it. The Sprint Goal also creates coherence and focus, encouraging the Scrum Team to work together rather than on separate initiatives.

The Sprint Goal is created during the Sprint Planning event and then added to the Sprint Backlog. As the Developers work during the Sprint, they keep the Sprint Goal in mind. If the work turns out to be different than they expected, they collaborate with the Product Owner to negotiate the scope of the Sprint Backlog within the Sprint without affecting the Sprint Goal.

Three pillars uphold every implementation of empirical process control: transparency, inspection, and adaptation.

Three pillars uphold every implementation of empirical process control: transparency, inspection, and adaptation.