What are the products formed when ammonium dichromate is thermally decomposed?

Identify the incorrect statements about group $15$ elements :
$A$. Dinitrogen is a diatomic gas which acts like an inert gas at room temperature.
$B$. The common oxidation states of these elements are $-3, +3$ and $+5$.
$C$. Nitrogen has unique ability to form $p\pi-p\pi$ multiple bonds.
$D$. The stability of $+5$ oxidation states increases down the group.
$E$. Nitrogen shows a maximum covalency of $6$.
Choose the correct answer from the options given below.

White phosphorus $P_{4}$ has the following characteristics:

Which of the following oxides of nitrogen is a mixed anhydride of two acids?

Which one of the following combines with $Fe(II)$ ions to form a brown complex?

Which element does not form complexes?