If you have a Sketchup Document in a newer version of Sketchup and you cannot save the sketchup document in the newer version to an older version of sketchup because you don’t have the newer version of sketchup or because of some other reason; then try this method it may work; it have worked for me:
Step 01: Go to the sketchup file you wish to open to the older version and right click on it and click on properties
Step 02: On properties where it says Open with click on Change
Step 03: Navigate to the desktop or folder where the icon of the older version of the sketchup is located click on it and click OK, then click Apply, then close the dialog box by clicking OK
Step 04: Go to the file that is changed to open in an older version of Sketchup and either drag and drop it to the newer version of sketchup; or double click on it to open it; or open it using the open dialog option in the newer version of Sketchup.