Question

the joints between ribs and the breastbone allow slight movement true or false

Answer 1

yeah!! It's true... 'cause while we respire joints allow slight movement.
I hope it helps you...

Answer 2

As per human anatomy, the first and the last three ribs of the human body occupy a single synovial joint with just the corresponding vertebrae.

But this is not the case of the remaining ribs because they occupy double synovial joints.

The tubercles are absent for the 11th and the 12th ribs so there can be the possibility of a slight movement between the breast bone and the joints between ribs.