Is there a way to have both QGIS 3.0 and 2.18 installed on one computer but have 2.18 as the default Package when opening workspaces. At the moment 3.0 opens all my workspaces which is rather annoying as most of the Plugins and providers I'm using are not available yet in 3.0. It was more of a test download to familiarise myself with the newest version until it is brought up to LTR standard. OS is Windows 10
For standalone installations, go to
C:\Program Files\QGIS 2.18\apps\qgis\bin, for OSGEO4W64, to
C:\OSGeo4W64\apps\qgis-ltr\bin (not tested here, I only have QGIS 3.0 and qgis-dev in OSGEO4W64).
Doubleclick on qgis.reg, and the version will be used as default for opening .qgs files.