Couple ways actually, you can rollback from the CCC
right click
SONAR Platinum, select
"Rollback", cursor down to the install you want; they're all there!
or go the folder that has your
Command Center/Downloads; this is on your hard drive where ever you've
told SONAR to put your downloads.
if you haven't "tidied up" lately, you can just run the appropriate .exe from there.
Notice I have 2016.10 11 and 12 still on the drive.
HTH,
T