Identify the reagent used for replacement of $-\text{N}_2^+\text{Cl}^-$ from benzene diazonium chloride by iodine.

What is the product P obtained in following reaction?
$\text{CH}_3\text{CH}_2\text{Br} + \text{AgCN}_{(alc)} \rightarrow \text{P}$

What is action of $\text{CH}_3\text{ONa}$ on $\text{CH}_3\text{CH}_2\text{Br}$
$\text{CH}_3\text{ONa} + \text{CH}_3\text{CH}_2\text{Br} \rightarrow$ ?

Which of the following reagents limits the oxidation of $\text{R-CH}_2\text{OH}$ up to R-CHO only?