I say dig it back up in fall, yes you can prune it back, no idea about a cutting for it. What zone are you in? I do know that they are hardy up to 30 degrees. My Mandevilla in SC did come back, but if you are say in FL, TX, So Cal, it may over winter for you.
I'm in VA so we get pretty cold at times. I'll tackle digging it up in the fall. Thanks for the tip.
I was thinking about trying to root a stem into a pot of soil and starting a new plant.