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

Propene when treated with cold conc. $\mathrm{H}_2 \mathrm{SO}_4$ forms a compound which on heating with water gives

Identify the amine formed when ethyltrimethyl ammonium iodide is treated with silver hydroxide and further heated strongly

For a chemical reaction rate law is, rate $=k[A]^2[B]$. If $[A]$ is doubled at constant $[B]$, the rate of reaction