I am currently running the Mac After Effects CC 2017 (November 2016) Release. I would like to keep it on my system along with the newest (April 2017) release. Any suggestions on accomplishing this since the Creative Cloud installer wants to update it and not keep both copies? Want to be able to easily open past projects in the Nov release while starting new projects in the Apr 2017 release.
May I ask what you hope to accomplish by doing it this way?
No matter what CC 2017 release you are using, the project files will not be backwards compatible without the "Save As" step since they're all version 14.x as opposed to version 13.x that was the CC 2014 through CC 2015.3 releases. So I don't see why you would need the earlier version of CC 2017 to open older projects.
Anyway, to answer your question, you can't do what you are asking to do. You can have CC 2014, CC 2015, CC 2015.3, and CC 2017 all installed alongside each other as they are all separate versions. So, you could install CC 2015.3 (AE version 13.8), but CC 2017 is only one version no matter what the version number says. You can only have one CC 2017 installed.
Since there is no official way to run two versions of AE 2017, how hard of a process is it to revert back to my 14.0.1 version if I encounter problems? Just waiting for a break in my project schedule to test out the update to 14.2.