The chocolate on top can easily seal the entrance, as there are icings below the chocolates, preventing candies from falling down.
Combining two wrapped candies together is not easy.
If the chocolate consumes the whole top row, no new candies will spawn, and you will reach a game over if there are no matches left.
The orders are worth 29,900 points ((99 regular candies x 100 points per regular candy) + (15 special candies x 1,000 points per special candy) + (1 combination x 5,000 points per combination) = 29,900 points). Hence, additional 100 points is required to earn one star.