Which non-metal does not react with water but reacts with alkali?

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

Phosphorus forms a number of oxoacids. Out of these oxoacids,phosphinic acid $(H_3PO_2)$ has strong reducing properties. Write its structure and also write a reaction showing its reducing behavior.

Match the following:

Compound	Nature
$i$. $PbO_2$	$a$. Acidic
$ii$. $Sb_2O_3$	$b$. Basic
$iii$. $GeO_2$	$c$. Amphoteric

Heating $(NH_4)_2Cr_2O_7$ liberates a gas. The same gas is obtained by:

The general formula of alum is: