Which of the following statements is correct?

Consider the following reaction,
$2H_{2(g)} + 2NO_{(g)} \rightarrow N_{2(g)} + 2H_2O_{(g)}$
which follows the mechanism given below:
$2NO_{(g)} \underset{k_{-1}}{\stackrel{k_1}{\rightleftharpoons}} N_2O_{2(g)}$ (fast equilibrium)
$N_2O_{2(g)} + H_{2(g)} \stackrel{k_2}{\rightarrow} N_2O_{(g)} + H_2O_{(g)}$ (slow reaction)
$N_2O_{(g)} + H_{2(g)} \stackrel{k_3}{\rightarrow} N_{2(g)} + H_2O_{(g)}$ (fast reaction)
The order of the reaction is

During the kinetic study of the reaction $2A + B \rightarrow C + D$,the following results were obtained:

Experiment	$[A] \ (M), [B] \ (M)$ and Initial rate of formation of $D$
$i. \ [A]=0.1, [B]=0.1$	$6.0 \times 10^{-3} \ M \ s^{-1}$
$ii. \ [A]=0.3, [B]=0.2$	$7.2 \times 10^{-2} \ M \ s^{-1}$
$iii. \ [A]=0.3, [B]=0.4$	$2.88 \times 10^{-1} \ M \ s^{-1}$
$iv. \ [A]=0.4, [B]=0.1$	$2.40 \times 10^{-2} \ M \ s^{-1}$

Based on the above data,the overall order of the reaction is:

For the reaction $A + B \rightarrow$ product,the rate of reaction is $3.6 \times 10^{-2} \ mol \ dm^{-3} \ sec^{-1}$. When $[A] = 0.2 \ mol \ dm^{-3}$ and $[B] = 0.1 \ mol \ dm^{-3}$,find the rate constant of the reaction if it is second order with respect to both reactants.

The following results have been obtained during the kinetic studies of the reaction: $2 \ NO + 2 \ H_2 \longrightarrow N_2 + 2 \ H_2O$

Expt	$\frac{-d[NO]}{dt} \ (mol \ L^{-1} \ s^{-1})$	$[NO] \ (mol \ L^{-1})$	$[H_2] \ (mol \ L^{-1})$
$1$	$4.8 \times 10^{-5}$	$1 \times 10^{-2}$	$1 \times 10^{-3}$
$2$	$43.2 \times 10^{-5}$	$3 \times 10^{-2}$	$1 \times 10^{-3}$
$3$	$86.4 \times 10^{-5}$	$3 \times 10^{-2}$	$2 \times 10^{-3}$

For a fourth-order reaction,what is the unit of $K$?