Which of the following is an elementary reaction?

Which of the following statements is true regarding the order of a reaction?

For the reaction,$2N_2O_5 \to 4NO_2 + O_2$,the rate and rate constant are $1.02 \times 10^{-4} \ mol \ L^{-1} \ s^{-1}$ and $3.4 \times 10^{-5} \ s^{-1}$ respectively. The concentration of $N_2O_5$ in $mol \ L^{-1}$ will be:

If the value of the rate constant $K = 2.3 \times 10^{-5} \ L \ mol^{-1} \ s^{-1}$,then identify the reaction order:

For a reaction between substances $A$ and $B$,the rate law is given by: $\text{Rate} = K[A]^n[B]^m$. If the concentration of $A$ is doubled and the concentration of $B$ is halved,what will be the ratio of the new rate to the original rate?

For the reaction $2 NO_{(g)} + Cl_{2_{(g)}} \rightarrow 2NOCl_{(g)}$,when the concentration of $Cl_2$ is doubled,the rate of the reaction becomes twice the original rate. When the concentration of $NO$ is doubled,the rate becomes four times the original rate. What is the overall order of the reaction?