Why can’t molecularity of any reaction be equal to zero?

For a chemical reaction,$m A \rightarrow x B$,the rate law is $r = k[A]^{2}$. If the concentration of $A$ is doubled,the reaction rate will be,

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

The reaction $2FeCl_3 + SnCl_2 \rightarrow 2FeCl_2 + SnCl_4$ is an example of a .......

$A_2 + 2 \, B \to 2 \, AB$

$[A_2]$	$[B]$	$-d[A_2]/dt$
$0.1$	$0.2$	$1 \times 10^{-2} \, M \, s^{-1}$
$0.2$	$0.2$	$2 \times 10^{-2} \, M \, s^{-1}$
$0.2$	$0.4$	$8 \times 10^{-2} \, M \, s^{-1}$

The order of reaction with respect to $A_2$ and $B$ are respectively:

Which one of the following statements regarding the order of a reaction is not correct?