I usually see them for sale at about 3 months and older. If you are new to chameleons don't buy anything younger IMHO. They can eat basicly anything (size wise) as the length of the space between their eyes. Flightless fruit flies, pinhead crickets would be most popular choices.
Plus yor picture have veild in it, they are called Yemen as the area they coming from and their humidity requirements are low (they can live in high moisture environment as they adapt, like here in Fl) but they naturaly live in more of a dry bushes then lets say panthers in Madagascar.
Well little damp substrate will keep moisture high, which your cham will like, but 2 litters in a day seems a lot. He will not go there as he stay in branches but later on all that heat and moisture......I'll be afraid of something start growing there, wouldn't be to good, I will place something...
When I get mine, guy told me, bean beetles fed baby, well....it eats crickets now because that's what I have for now, before my roaches and superworms take off, and no problem, I'm sure that it will go the other way around, from crickets to something else, and as MissSkittles pointed out, yes he...
Man I thought I did pretty good research before getting hooked on the most beautiful reptile out there, but just like with anything the more you know, the more you finding out how little you actually know, so please do it, that will be awesome.