1) Beardie's under ideal condition can grow up to 1" a week from 6 - 16" then growth slows down. But some beardies grow slower too. Hard to say. Most of the growth happens in the first year but they may get an inch longer to the 2nd year. Seems most US beardies top out at about 20" or so. I have heard of but never seen beardies to 24" or so.
2) I don't like the idea of putting males in with females unless you have a very large outside enclosure. If I had to do it I'd go 8 x 2 or 3 with basking areas on each side and the cool part in the middle. 6 X 2 is fine for 2 or 3 females.
3) http://www.dachiu.com/sexing.html
4)That's debatable. Normals or cross normals are the hardiest in my opinion. Fancy colored dragons are bred for one thing - Color.
5) Greens & Vegs.
http://www.beautifuldragons.503xtreme.com/Nutrition.html
Feed babies and juveniles all greens (no veg.). Torn to smaller than their head. Mist well. Small amounts of fruit are fine. Just no avocado.
Live food
Crickets (bodies smaller than the space between your dragons eyes) Silkworms & Silkworm Moths, appropriately sized captive bred roaches. I don't do mealworms, waxworms, butterworms, or superworms. But all appropriately sized are acceptable as treats. No mealworms except for adult dragons.