The features that are released but not yet ready for the wide use are protected by the experiment. The developers and users can opt-in into these features before they are fully released.
The Experiments UI to enable or disable experiments for the content served from https://cdn.ampproject.org is available at:
https://cdn.ampproject.org/experiments.html
For content served from any other domain, experiments can be toggled in the devtools console when development mode is enabled using:
AMP.toggleExperiment('experiment')