Google has put up its own webpage containing full length of information, description and revelation for the Android O. This is the webpage for Android O Developer Preview, which informs all what to expect as well as details the hows in migrating from the previous Android operating system to Android O. The webpage also provides app downloads to test Android O.
The Android O Developer Preview website has link page Program Overview, and especially the page Key Developer Features where the vital information are provided such as notifications, autofill framework, picture mode, fonts, adaptive icons, color management, wi-fi aware, device pairing, webview APIs, pinning shortcuts and widgets, accessibility, permissions, and more up to Java programming language updates. Besides, it has pages for Downloads, Migrating Apps to Android O, Android O Behavior Changes, Android O Features and APIs, Code Samples, Feedback page, and Downloads, with sub links- Manually flashing a device, and Uninstalling.
The Downloads page of the Android O Developer Preview website has only downloadables of system images for a range of hardware devices which can be used for testing apps from phones to tablets and TV. But these are most intended for developers only and enthusiastic users wanting to get a first taste of Android O are most warned that it is on their own risk if they proceed trying it without the Android O owner answering for liabilities in case of the system destruction in the users' phones.
To be able to test Android O, the system image should first be downloaded and then flashed to the device. Then they just have to follow the Program overview for timelines and migration guide for steps to compatibility and building for Android O. Presto, if there's no hitch, the phone using the previous Android system would be updated to the latest milestone build. But caution: This is only an Android O Developer Preview No. 1, which is first for developers only and not intended for daily or consumer use.