In my previous post, I wrote about alternatives to numbering sprints
Keep any "project before the project" as lightweight as possible. Most development projects do not need a project before they begin.
Remain true to the principles of Scrum. A team participating in a project before the project will not be able to have anything potentially shippable. That's fine. But understand why having something potentially shippable is a central tenet of Scrum and apply that in a honest way to the project before the project.