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

Ammonia is not produced in the reaction of

The following are some statements related to $VA$ group hydrides:
$I$. Reducing property increases from $NH_3$ to $BiH_3$.
$II$. Tendency to donate lone pair decreases from $NH_3$ to $BiH_3$.
$III$. Thermal stability of hydrides decreases from $NH_3$ to $BiH_3$.
$IV$. Bond angle of hydrides decreases from $NH_3$ to $BiH_3$.
The correct statements are:

The most acidic among the following compounds is

The nitrogen oxide$(s)$ that contain$(s)$ $N-N$ bond$(s)$ is(are):
$A$. $N_2O$
$B$. $N_2O_3$
$C$. $N_2O_4$
$D$. $N_2O_5$

Dilute nitric acid on reaction with silver liberates