Below is the development process I have followed at SimpleTouch for many years and after many years of refinement.
The product has a high-level roadmap that is a 6-12 month vision of the product. This sets the long-term direction of the development process.
Work is done in iterations of 2-6 weeks, preferring shorter iterations. Each iteration is a "Release".
Before each release, a Release Roadmap is planned, a short description of the work to be done in the Release and is driven by the Product Roadmap.
Planning a Release
Each release is planned to develop the Product Roadmap. The following is a guideline for that process, including the initial development phase.
Each release has a sprint for that release with a start and end date. The sprint name is the version of the release or "Next Release" for the upcoming release. Bugs, features, and tasks are assigned to a sprint and are assigned a priority.
Phases of Development
A release goes through several phases. Planning, development, Beta, Testing, and release as shown below. It is possible that simultaneous versions can be in each phase.