O.K... it's impossible.
No one keeps up with all the changes, however we can try to stay on top of the changes that affect what we do and how we do it. One of the nice changes I saw recently was a training push by Texthelp... the good folks who created Read & Write for Google Chrome, They have created a training portal on their site to help you walk through how to get the most out of Read & Write for you and your students. This fundamentals course covers use of R & W in Google Docs, in the web toolbar and in PDFs and ePubs. They have also updated their quick reference guide- downloadable here.
Explore - New functionality across Google Docs, Sheets and Slides
This just came out last week. You can read more about it here. Essentially the goal is to make you work more productively. However, there is already a hue and cry in the edtech edu sector because the research tool in Google Docs has "disappeared". The explore button does some of what the Research Tool did, but you cannot search easily for dictionary meanings or quotes. The ability to search for images by license is missing. However it does return images which seem to be copyright-free, but it also sticks the attribution right under the image instead of in the footnote. It looks like you will need to use Easybib or Noodle Tools, etc. to build the bibliography as that is also missing from the explore button. So, either they will respond the numerous complaints they are getting online, or we can get used to a different, "improved" version.
The functionality improvements in Sheets look pretty cool. It looks like they are continuing to try to make working with data easier and more intuitive, allowing questions in more natural language. You can read more about them here. John Sowash created a quick overview of the Explore button in sheets. Richard Byrne also created a little video about the changes in Google Slides.