Google’s Webmaster Trends Analyst John Mueller (@JohnMu) answers a question about using Structured Data Properties from schema.org vs Google developers documentation.
We need to use structured data as per the Google Developers site (including required/recommended properties) or can we use more properties from Schema.org apart from the Developers site?
Google use Structured Data in search for both supporting Rich Results types as well as for better understanding the pages themselves.
In order to be eligible to be shown as a Rich Result, you need to make sure that the page uses the right Structured Data, and that is complies with the appropriate policies on our site.
However, even without the Structured Data leading to Rich Results, our systems profits by understanding the pages better when they use Structured Data.
Also, keep in mind that is not guaranteed for us to show these Rich Results just because the page uses the appropriate Structured Data.
In short; if you mean to be eligible for specific Rich Results type in Google search, then you should definitely watch out for the requirements.
Independently; you are always welcome to use Structured Data to provide better macchine language readable contexts for your pages, which may not always results in visible changes, but can still help our systems to show your pages for relevant queries.