Which of the following reactions is a termolecular reaction?

The reaction $N_2O_5$ (in $CCl_4$ solution) $\to 2NO_2$ (solution) $+ \frac{1}{2}O_{2(g)}$ is of first order in $N_2O_5$ with rate constant $6.2 \times 10^{-1} \, s^{-1}$. What is the value of the rate of reaction when $[N_2O_5] = 1.25 \, mol \, L^{-1}$?

Why is molecularity applicable only for elementary reactions,while order is applicable for both elementary and complex reactions?

For the reaction $Cl_{2(aq)} + H_2S_{(aq)} \to S_{(s)} + 2H^{+}_{(aq)} + 2Cl^{-}_{(aq)}$,the rate law is $r = K[Cl_2][H_2S]$. Which of the following mechanisms is/are consistent with this rate law?
$A. \ H_2S \rightleftharpoons H^{+} + HS^{-}$ (fast)
$Cl_2 + HS^{-} \to 2Cl^{-} + H^{+} + S$ (slow)
$B. \ Cl_2 + H_2S \to H^{+} + Cl^{-} + Cl^{+} + HS^{-}$ (slow)
$Cl^{+} + HS^{-} \to H^{+} + Cl^{-} + S$ (fast)

The rate law equation for a reaction between $A$,$B$ and $C$ is $r = k[A][B][C]^2$. What will be the new rate of reaction if the concentration of both $A$ and $B$ are doubled (in $r$)?

The conversion of molecules $X$ to $Y$ follows second order kinetics. If the concentration of $X$ is increased to three times,how will it affect the rate of formation of $Y$?