Which one of the following statements is correct for a reversible reaction? $A$ catalyst

At equilibrium for the reaction $A_{2(g)} + B_{2(g)} \rightleftharpoons 2 AB_{(g)}$,the concentrations of $A_2$,$B_2$,and $AB$ respectively are $1.5 \times 10^{-3} \ M$,$2.1 \times 10^{-3} \ M$,and $1.4 \times 10^{-3} \ M$ in a sealed vessel at $800 \ K$. What will be $K_p$ for the decomposition of $AB$ at the same temperature?

For the gas phase reaction; $C_2H_{4(g)} + H_{2(g)} \rightleftharpoons C_2H_{6(g)}$,$\Delta H = -32.7 \ kcal$ carried out in a vessel,the equilibrium concentration of $C_2H_4$ can be increased by:

Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as:
$CH_3COOH_{(l)} + C_2H_5OH_{(l)} \longleftrightarrow CH_3COOC_2H_{5(l)} + H_2O_{(l)}$
$(i)$ Write the concentration ratio (reaction quotient),$Q_c$,for this reaction (note: water is not in excess and is not a solvent in this reaction).
$(ii)$ At $293 \ K$,if one starts with $1.00 \ mol$ of acetic acid and $0.18 \ mol$ of ethanol,there is $0.171 \ mol$ of ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant.
$(iii)$ Starting with $0.5 \ mol$ of ethanol and $1.0 \ mol$ of acetic acid and maintaining it at $293 \ K$,$0.214 \ mol$ of ethyl acetate is found after sometime. Has equilibrium been reached?

The dissociation of $CO_2$ is represented as $2CO_2(g) \rightleftharpoons 2CO(g) + O_2(g)$. If $2 \ mol$ of $CO_2$ are taken initially and $40\%$ of $CO_2$ dissociates,what will be the total number of moles at equilibrium?

$K_{c}$ for the following reaction is $99.0$: $A_{2(g)} \rightleftharpoons B_{2(g)}$. In a $1 \ L$ flask,$2 \ moles$ of $A_{2}$ were heated to $T(K)$ and equilibrium was reached. The concentrations at equilibrium of $A_{2}$ and $B_{2}$ are $C_{1}(A_{2})$ and $C_{2}(B_{2})$ respectively. Now,$1 \ mole$ of $A_{2}$ was added to the flask and heated to $T(K)$ to establish equilibrium again. The concentrations of $A_{2}$ and $B_{2}$ are $C_{3}(A_{2})$ and $C_{4}(B_{2})$ respectively. What is the value of $C_{3}(A_{2})$ in $mol \ L^{-1}$?