Total AE N00b here ...
I assume that AE version 12.0x353 is creative cloud?
Is there any way to open newer versions of .aep files in standard CS6 versions of AE?
No, you can't open After Effects CC (12.0) projects in After Effects CS6 (11.0).
You can open an After Effects CC (12.0) project in After Effects CC (12.0) and then use a command to save the file as a version that can be opened by After Effects CS6 (11.0):
File > Save As > Save A Copy As CS6