1. Release management planning occurs with every Sprint Planning, Sprint Review and refinement activities that are undertaken. You plan for the duration of a Sprint and adjust the plan based upon new information discovered.
2. How often do you need or want to deploy code to production? There is nothing in the Scrum framework that states any rules, restrictions or best practices. The one possible exception to my previous sentence is that anything considered "done" has to meet the Definition of Done. But that is a stretch because any increment can be deployed when the Scrum Team determines that it should be.