The role of a catalyst in a reversible reaction is to

For the reaction $aA + bB \rightleftharpoons cC + dD$,if the equilibrium shifts in the backward direction at low pressure and high temperature,which of the following is correct?

For the reaction $A_{2(g)} + B_{2(g)} \rightleftharpoons 2AB_{(g)}$; $\Delta H = +ve$,which of the following statements is correct regarding the effect of pressure?

According to Le Chatelier's principle,adding heat to a solid and liquid in equilibrium with an endothermic nature will cause the:

For the following balanced reaction occurring at a constant temperature,what will be the change in the concentration of $CO$ if the volume of the system is decreased?
$2CO_{(g)} \rightleftharpoons O_{2(g)} + 2CO_{2(g)}$

Consider the following reversible reaction at equilibrium,$2H_2O_{(g)} \rightleftharpoons 2H_{2(g)} + O_{2(g)}$; $\Delta H = 241.7 \ kJ$. Which one of the following changes in conditions will lead to maximum decomposition of $H_2O_{(g)}$?