I think I just have the "plain" 1222, no letters after the model number. Is IDT the same as dual feed, the same as walking foot? I certainly do not have a thread cutter that I know of. Or, come to think of it, maybe I do and just don't use it...a little V-shaped metal piece?
For the moment I have decided to just stay with the feet I have, not buy an adapter and snap-on feet. It is good to know I could, though!
The help on this website is just amazing, and I am grateful as always.