Hi,
As the functionality development and enhancement is a incremental process for any product development , so the best options is to go through all release note and new features for all the version of dynamic 365. You may find many blogs and article , MS documents by web search , google search . Its hard to collect all together in a single post .
You can search using following combination replacing the year and version number-
"Whats new in Dynamics CRM 2013"
"Release note Dynamics 365 9.0" ,
"Dynamics CRM 2016 new features"
Hope this helps.