To downgrade to an earlier version of iTunes, download the version you want. A good resource is:
http://www.oldapps.com/downloadiTunesmac.php
And you need to do the following:
Go to your hard drive >Library >Receipts and trash the iTunesX.pkg.
Next, drag your iTunes application to the trash.
Backup your iTunes Library file and .xml files and any iTS purchases.
Repair permissions in Disk Utility, then install the desired version of iTunes. Repair permissions again.
Open the iTunes app. If everything looks good, you can empty the trash.
I suspect that in your earlier attempt you did not trash the pkg.