Which reaction is useful for the exchange of halogen in alkyl chloride by iodide?

For a given alkyl group,the densities of the halides follow the order:

What is obtained when nitric acid reacts with chloroform?

$CH_3 - CH_2 - CH_2Br + KOH$ (alc.) $\to$ Product
The product in the above reaction is:

Chloroform for anesthetic purposes is tested for its purity with the reagent

$A$ bottle containing $C_6H_5I$ and $C_6H_5CH_2I$ has lost its label. To identify them,samples $A$ and $B$ are taken in separate test tubes and boiled with $NaOH$ solution. Finally,the solution in each test tube is acidified with dilute $HNO_3$ and then a few drops of $AgNO_3$ solution are added. Substance $B$ gives a yellow precipitate. Which statement is correct for this process?