I just watched the PV for Kanashiki Heaven on JPopsuki TV. It was so cool, and they all looked so lovely.
There wasn't really that much of a change. Once again, it was just a duet with Airi and Chisato while the others were their backups.
It's probably called the "Single ver." because it was updated as such for the double A-side.
Edit:They showed it on Hello! Station(after a long hiatus) Check out how they amped it up!
Starts at
4:14