In which of the following compounds, nitrogen exhibits the highest oxidation state?

The following are some statements related to $\mathrm{VA}$ group hydrides.

$\mathrm{I}.$ Reducing property increases from ${\mathrm{NH}}_{3 }\mathrm{to} {\mathrm{BiH}}_3$

$\mathrm{II}.$ Tendency to donate lone pair decreases from ${\mathrm{NH}}_3 \mathrm{to} {\mathrm{BiH}}_3$

$\mathrm{III}.$ Thermal stability of hydrides decreases from ${\mathrm{NH}}_{3 }\mathrm{to} {\mathrm{BiH}}_3$

$\mathrm{IV}.$ Bond angle of hydrides decreases from ${\mathrm{NH}}_3 \mathrm{to} {\mathrm{BiH}}_3$

The correct statements are