When I open IDLE it is version 3.4.0. I know that I have Python 2.7.6 installed on my system as well. How can I open the IDLE interface for this version?
If you can start python2.7 in a terminal, you should be able to run its version of IDLE by adding option -m idlelib.idle to the startup command. Details depend on your system.
If you can start IDLE with an icon, you should be able to copy the icon and change the python version from 3.6 to 2.7 in the icon properties. Again, detail depend on your system.