Hi - This video (which I just discovered today) features an excellent illustration of point (a) in the prior reply to your question. Hope it helps - good luck! :)

Hi - Maybe a professional might see this question and reply, but in the interim, as merely a fellow Grokker user, I would offer two possible modifications/substitutions:
(a) when lying on your back, instead of doing exercises that lift your back, neck and head, maybe keep your upper body on the floor and lift your legs instead. The higher the legs, the easier the ab work; the lower the legs, the harder.
(b) if you choose to lift your torso, neck and head, maybe keep one or both hands behind your head at all times - no matter where the teacher's hands are - to support your head and avoid neck strain.
Be gentle and kind to your body and progress slowly and steadily, avoiding all pain and strain. Best wishes! :)