For which element would $XH_3$ be a stable species?

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:

Strong reducing behaviour of $H_3PO_2$ is due to

$A$ colourless gas with the smell of rotten fish is

$FeSO_4$ gives a brown ring with ........

Identify the $INCORRECT$ statement$(s)$ among the following:
$(I)$ Moist ammonia gas can be dried by using anhydrous $CaCl_2$
$(II)$ Phosphine is a weaker base than ammonia
$(III)$ $R_3SiCl$ produces very complex cross-linked polymeric silicone on hydrolysis
$(IV)$ When metallic copper reacts with $6 \ M$ $HNO_3$,$NO_2$ is the only product