Crossrail changes its staged opening plans

Although the opening of Crossrail is the public deadline that keeps shifting, it is in fact only the 3rd stage of a 5-stage process, and how the final two stages will be carried out has been changed.
The changes are generally good for passengers and will see the final phase of opening the full line delivered sooner than currently planned.
Current service
Stage 1 (May 2015)
TfL Rail branded service running between Liverpool Street and Shenfield. The Elizabeth line trains started replacing the old