I responded to your question a few days ago regarding catching left and right button presses. Use the same technique, and try catching the down button press on the last button, and then focus on the first button. I'm not positive this will work with the spatial navigation, but I believe it should.

I would verify with Yahoo whether this kind of functionality will be allowed as it sounds like this will prevent a user from navigating to the bottom widget control/color buttons using the arrow buttons. It may be allowed as they can press the colored buttons on the remote. We have stayed away from creating anything that alters the typical spatial navigation flow.

Stopping spatial navigation from reaching either the top header bar or the bottom color buttons is not allowed and you will be rejected during the QA process.

I think looking into a Grid instead of 13 buttons would be the best path based on your description.

how to update new list of buttons on the same side bar.