Development Stage: When a new branch of Drupal is opened for development after the release of newest version of Drupal, development phase has been begins. At the time of development phase, many new features as well as changes are considered for acceptance as long as core’s technical debt is within the issue doorsills.
One can easily re-write the entire form API, add modules to core and remove modules from core, add & remove template files and changes API as fix discrepancies have always exasperated you. People decrease the reach of the patched that are accepted after the development stage ends.
Mainly, the aim of the new version of Drupal toward a releasable state while it is under development and so users shun changes that are mainly introducing technical debt or other risks to a timely release.
Feature conclusion Stage:
When it comes to feature conclusion stage, it has been extended between two major free deadlines like an initial feature freeze deadline and feature completion deadline. Some major features and refactoring that are already under development may be accepted after the primary feature freeze deadline.
Until the next main Drupal version, the features as well as refactoring that are not already under development can be postponed for some time. At the maintainer’s judgment, some minor features can be accepted as issue counts are under thresholds. During the feature completing stage, API changes are still allowed. However, Drupal 8’s feature completing stages lasted from December 1, 2012 to February 18, 2013.
Cleaning Stage and Alpha Releases:
Once the feature completion deadline, a clean-up stage begins. At this stage,
API changes are still allowed till the API solidifies the deadline, so they do not significantly boost the overall technical debt.
Publishing alpha releases at the time of clean-up stage. However, it is also important that alpha releases should be measured as unreliable. Alpha releases should be considered unstable and unreliable. They are intended for testing and contributed module development only.
One of the most important points of alpha releasing is to enable module developers to recognize API lacks while they can still be corrected. Improving from the previous stable version of Drupal to an alpha release is not reliable. Production websites should not use alphas as the risk of data loss.
Stage of API conclusion and beta releases:
After the API freeze deadline, the API completing stage begins. The main purpose of this stage is to resolve release-blocking issues, and backwards compatibility. The changes of API enable when they are needed to fix important and critical bugs and tasks. July 1, 2013 was the date of API freeze for Drupal 8. The API freeze date for Drupal 8 was July 1, 2013. From this point, the issue sills are reduced weekly. See the API completion phase issue queue thresholds for more information.
At the Time of API completion stage, publishing of beta releases has been carried out. Once the core data model is completed and APIs are stable, the beta releases.
At the time of their stage to uncover critical API, contributed modules as well as theme developers are really positive to stat porting their module. However, it can be also corrected, but they should be aware about APIs that it still changes as some decisive issues are addressed.
Along with it, one needs to wait for the first release candidate as developers, who are looking to go through the upgrade process. Generally, a data relocation path is not offered between beta releases. Between release, user interface and translate strings may also changes.
These are some of the major update information that will be beneficial for you. If you are not getting these updates, it is recommended to you to hire a professional Drupal developer.