According to the Scrum Guide, two things that the Scrum Team should do during the first Sprint are building at least one piece of valuable functionality and creating at least one valuable, useful Increment. These are the goals of every Sprint, regardless of its order. The other options are not things that the Scrum Team should do during the first Sprint, as they are either out of scope (such as defining major product features and a release plan architecture or making a plan for the rest of the project) or unnecessary (such as analyzing, describing, and documenting requirements for subsequent Sprints).