Can you see the curl at the end of his tail? That's how it will look if it is a girl. If is just a few feathers that are curled.
This is a girl. She has no curl at the end of her tail.
So that's the difference between the girls tail and the boys :D
1. It really depends. One of my ducks was about 6 weeks. And the rest of the girls were about 2 months when they started to quack. It seems like it took a lot longer than expected for the boys to get their quack. They were about five months.
2. I said before, that it took five months for the...