Refactoring metaphor is the change of oil in the garage. If you don't do it after each car than the cleaning afterwards becomes very difficult of even impossible. Keeping your internal structure of the code base clean is an important best practice in XP programming. It will provide you with a code that can be easily maintained.
The product owner is a key role most of the time fullfilled by an empowered customer to decide on what the business wants and to prioritise in which order so that maximum business value can get implemented within the agreed budget. This role is preferrable a full time role and this person should sit within the team as part of the team.
The scrum process. Scrum is an iterative and incremental agile software development method for managing projects and accelerating new product development. Although scrum began life in the software development industry it is now being adopted more widely.
Operations should work very close together with the scrum team in order that after each iteration a potential shippable product can be deployed in an automated way towards the different test environments and the production environment. Dev Ops is a new agile practice where developers and Operations people works close together to deliver an end-to-end automated deployment process.