Technique wise you were probably doing it correctly for Veena and Neena's style, but probably not correctly for whatever style your teacher is teaching.
For your belly rolls try bending/slouching over in a chair and roll/pull in the top muscle of your abdomen. While doing this look for a triangle right under your ribs. When you find it, stand up and try rolling your belly the same as you did in your chair when you found the triangle. If you find the triangle again , your doing it correctly. Don't try it too much or you'll hurt yourself.
Sitting in front of a mirror helps too.
Please excuse my sorry diagram.
