$NH_3$ gas is not liberated by which of the following combinations?

In an Ostwald process:
$NH_3 + O_2 \xrightarrow[Pt]{\Delta} x + H_2O$
$x + O_2 \to y$
$y + H_2O (excess) \to x + z$
The incorrect option is:

$A$ obtained by Ostwald's method involving air oxidation of $NH_3$,upon further air oxidation produces $B$. $B$ on hydration forms an oxoacid of Nitrogen along with evolution of $A$. The oxoacid also produces $A$ and gives positive brown ring test.

The reddish-brown coloured gas formed when nitric oxide is oxidised by air is

The total number of compounds having at least one bridging oxo group among the molecules given below is. . . . . . .
$N_2O_3, N_2O_5, P_4O_6, P_4O_7, H_4P_2O_5, H_5P_3O_{10}, H_2S_2O_3, H_2S_2O_5$

Nitrogen is a relatively inactive element because