Is this used for holding onto the curls so the hair doesn't frizz up after drying wet hair?

Yes, you have it put it on the hair when it's dry or slightly wet. Thank you

Does this product leaves residue or causes product buildup in the hair?

When I use this product I spray clean hair with distilled water and apply the cream. I rewatch after a week. Using this method it does not cause build up.

On a scale from 1-10, how moisturizing is this product?

My daughter's hair looks very moist when its just combed i.e when its wet. However by the next day the hair is dry. In my view it doesnt keep the hair moist.