Personally, I’m not a fan of XBMC’s “Kodi” rebranding, and my plugins so far do not work in versions past Gotham. As such, I have needed to stay behind in the development cycle to utilise the tools I have come to know and love. (Much like OSX Mavericks over Yosemite.)
For Windows and OSX, you can easily download and install the proper binary directly from the XBMC archive.
To install previous versions of Kodi in Linux, you simply have to specify the version number when you execute the install command:
sudo apt-get install xbmc=2:[INSERT VERSION NUMBER HERE]* xbmc-bin=2:[INSERT VERSION NUMBER HERE]*
For Kodi versions (beyond 13.2), replace xbmc with kodi for both packages.
For a list of available versions, execute the following:
sudo apt-cache policy xbmc
sudo apt-cache policy kodi
For more information, consult the Kodi wiki.