The sperm and the egg would contain different copies of the chromosomes. The cell randomly divides its chromosomes when it becomes an egg or sperm. When they merge, two halves of a genome form a full one again. But some chromosomes would be there as doubles, others would be lost. The effect would be the same as incest. Mutations that would be hidden in a healthy cell would emerge.

No, it is something different. Cloning creates a another being with the exact same DNA. This would allow people, who can’t produce viable sperm/egg cells, to reproduce with their partner. First patients would be infertile men and women.