What is the unit of the rate constant for a $4^{th}$ order reaction?

For the reaction $2H_2 + 2NO \to N_2 + 2H_2O$,the following mechanism has been proposed:
$I$. $2NO \rightleftharpoons N_2O_2$ (fast)
$II$. $N_2O_2 + H_2 \xrightarrow{k_2} N_2O + H_2O$ (slow)
$III$. $N_2O + H_2 \to N_2 + H_2O$ (fast)
What will be the rate law of this reaction?

The rate of the reaction,$CH_3COOC_2H_5 + NaOH \longrightarrow CH_3COONa + C_2H_5OH$ is given by the equation,$\text{rate} = k[CH_3COOC_2H_5][NaOH]$. If concentration is expressed in $mol \ L^{-1}$,the unit of $k$ is

What is the relationship between the half-life period $(t_{1/2})$ and the initial concentration $([R]_0)$ for a reaction of order $n$?

Write the equation for a pseudo first order reaction. Write the rate law and the rate constant.

The reaction of hydrogen and iodine monochloride is given as
$H_{2(g)} + 2ICl_{(g)} \to 2HCl_{(g)} + I_{2(g)}$
This reaction is of first order with respect to $H_{2(g)}$ and $ICl_{(g)}$. Which of the following mechanisms is consistent with the given information?
Mechanism $A$:
$H_{2(g)} + 2ICl_{(g)} \to 2HCl_{(g)} + I_{2(g)}$
Mechanism $B$:
$H_{2(g)} + ICl_{(g)} \to HCl_{(g)} + HI_{(g)}$ (Slow)
$HI_{(g)} + ICl_{(g)} \to HCl_{(g)} + I_{2(g)}$ (Fast)