2/ Scrum : what, when and how ?
3/ XP : what, when and how ?
4/ Kanban : what, when and how ?
5/ Scrum vs Kanban.
Scrum and XP are the best-suited methodologies for project building phase.
Kanban is best for production support phase (resolve issues as soon as possible without waiting a sprint to be defined or writing for new tests to be implemented).
If you know very well the product, you have a clear and certain specifications (product backlog and stories) and you have the needed actors (a product owner and a scrum master), scrum is the best-suited for an iterative and progressive project build.
Scrum’s roles, events, artifacts, and rules are immutable and although implementing only parts of Scrum is possible, the result is not Scrum. Scrum exists only in its entirety and functions well as a container for other techniques, methodologies, and practices.
XP doesn't conduct complete up-front analysis and design--an XP project starts with a quick analysis of the entire system, and XP programmers continue to make analysis and design decisions throughout development.
XP is a lightweight methodology for small to medium sized teams developing software in the face of vague or rapidly changing requirements. -Kent Beck-
XP resolve the "begin fast" by pushing to extreme quality mesure tools like Continuous Integration, unit test, TDD, refactor, ... keeping all of the tests running at all times.
Choose the right methodology that suit to your case but don't break the rules.