At what temperature is white phosphorus heated to obtain red phosphorus (in $K$)?

Which of the following statements is $NOT$ true?

How can you synthesise nitric oxide in the laboratory?

$P_2O_3 + H_2O \rightarrow X$
$Red \ P_4 + \text{alkali} \rightarrow Y$
$X$ and $Y$ are oxoacids of phosphorus. The number of $P-OH$ bonds in $X$ and $Y$ respectively is:

Why does nitrogen show catenation properties less than phosphorus?

The gas which is absorbed by ferrous sulphate solution giving blackish brown colour is