Which of the following statements is NOT correct regarding order of reaction?

What is half life of a first order reaction if time required to decrease concentration of reactant from 0.4 M to 0.1 M is $x$ hour?

For the reaction,

$$ 2 \mathrm{~N}_2 \mathrm{O}_{5(\mathrm{~g})} \longrightarrow 4 \mathrm{NO}_{2(\mathrm{~g})}+\mathrm{O}_{2(\mathrm{~g})} $$

$\mathrm{N}_2 \mathrm{O}_5$ disappears at a rate of $x \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{~s}^{-1}$

Find the rate of formation of $\mathrm{O}_2$ ?

A complex reaction takes place in following steps.

$$ \begin{aligned} & \mathrm{NO}_2 \mathrm{Cl}_{(\mathrm{g})} \longrightarrow \mathrm{NO}_{2(\mathrm{~g})}+\mathrm{Cl}_{(\mathrm{g})} \text { (slow) } \\ & \mathrm{NO}_2 \mathrm{Cl}_{(\mathrm{g})}+\mathrm{Cl}_{(\mathrm{g})} \longrightarrow \mathrm{NO}_{2(\mathrm{~g})}+\mathrm{Cl}_{2(\mathrm{~g})} \text { (fast) } \end{aligned} $$

Identify rate law equation for this reaction.