A Sprint could be canceled if the Sprint Goal becomes obsolete. Only the Product Owner has the authority to cancel the Sprint.

The Agile definition of done is a collection of criteria that must be completed for a project to be considered “done.” It is essentially a checklist used by Scrum teams to create a shared understanding of what is required to make a product releasable.

To fully understand the definition of done in the context of Scrum, we must first outline two of the key elements in Agile project management:

• Product backlog item: This is a specific improvement that is made to a product. Items can include bug fixes, user stories, and specifications.
• Product increment: This is what is produced at the end of a short development period or sprint. It combines all the product backlog items completed during this sprint.

In specific terms, the Scrum definition of done is a list of conditions that must be met to successfully mark a product increment as complete.

By definition, a Sprint cannot be longer than one calendar month. Therefore any so-called Sprint of a longer duration will be invalid, and it would mean that Scrum principles are not being followed.
Note that the Agile Manifesto allows up to two months between each delivery of customer value, albeit with a preference towards shorter timescales. Iterations of greater than a month may therefore be arguably agile, although they would not be Scrum-compliant.
Also, bear in mind that Scrum Sprints must result in *potentially* releasable increments and that the time between actual releases may therefore exceed one month. However, if the release of an increment equates to the delivery of customer value, and if the release is deferred for longer than two months, then the Scrum implementation (although strictly valid) would not conform with the principles of the Agile Manifesto.
Therefore be sure to time-box Sprints to no more than one month in length, and aim to release an increment into production at least every two.

As new information is learned, the team must negotiate with the Product Owner regardless of what it is. If the Developers feel strongly about something they think something needs adjusting, they are responsible for communicating the changes to the Product Owner before acting.

The output of a Sprint is a usable Product Increment. "Usable" means the stakeholders can see the product working as if it were released. The increment is the verified sum of all the Product Backlog Items completed during a sprint, plus all previous increments produced in the current and past sprints. Because of this, the increment needs to be integrated with the ones produced in past sprints. It must be in usable condition, regardless of whether the Product Owner decides to release it or not. The Product Owner is responsible for deciding when to release the Product Increment.

Only the Development Team can change its Sprint Backlog during a Sprint. If the Product Owner wants to change the work planned, he has to do this per the Development Team.

The Sprint Backlog is, ultimately, a plan for the Sprint. The development team executing work inside of a Sprint creates a Sprint Backlog. The creation occurs during the Sprint Planning. The central question is, how does this work get done? The Product Owner presents a list of prioritized items from the Product Backlog. The team will analyze the list, do capacity management, figure out what they can do, and make a plan to execute. The Sprint Backlog is a plan to achieve the overall goals of the Sprint.