From what I tested, you would have 12.6.5.3 installed in tandem to 12.9. I didn't bother trying sudo rm -rf /Applications/iTunes.app but Mac OS definitely doesn't let you delete the new iTunes from the GUI. I was fine with that as I would have just removed the new iTunes from the dock and put the old version on my dock. You have to extract the iTunes.app file from the 1.6.5.3 apk. Restore your iTunes library files from backup, then hold the option key down when you click on the iTunes 12.6.5.3 app. Choose your old library file and you're good. Right now I just reverted back to the new iTunes and will probably just use a VM and/or other apps like SuperImpactor for messing with old rolled back apps.