I am unaware of anything in science that has been formally proven.
It is the program controlling development that matters because everything has to be done in proper order.
Yes, the Hox genes encode for factors which are "master switches" for all of the accessories associated with a specific body part (i.e. leg, wing)
I am unaware of anything in science that has been formally proven.
Of course many things have been proven. Let's take a few - would you say that it has not been proven that the parents genes are not the source of the progeny's genes? Would you deny that that has not been proven? Would you deny that the Earth revolves around the Sun and the Moon around the Earth has not been scientifically proven?