a) Yes. The children hated Margot because they were jealous of her memories of the sun and because she was different from them. They bullied her and locked her in a closet just before the sun came out.
b) Yes. The story says that the children had been waiting for the sun to come out for seven years. They lived on Venus, where it rained constantly, and the sun appeared only once every seven years.
c) Yes. Margot was different because she had lived on Earth before moving to Venus, so she remembered seeing the sun. The other children had been born on Venus and could remember the sun only from books or lessons.