What are the differences between Dreamweaver_14_LS20.dmg and Dreamweaver_13_LS20.dmg? I find that there are two versions of Dreamweaver CC for Mac OSX, one is Dreamweaver_14_LS20 and another is Dreamweaver_13_LS20. Can anyone tell me what is the exactly differences between these two versions.

By the way, where can I download the full installer of Adobe Software on the official web site? I only find the CreativeCloudInstall which will download the others later.
Dreamweaver CC came in two major versions: the initial CC release (v13) and the CC 2014 release (v14). From the file names, you can infer which is which.

As for a "full installer", there is no such animal now. You install CC apps individually through the Creative Cloud Manager which downloads and installs the selected app(s).