Which of the following statements is true when equilibrium is established in the reaction? $A + B \rightleftharpoons C + D, K_C = 10$

In the figure shown below,reactant $A$ (represented by square) is in equilibrium with product $B$ (represented by circle). The equilibrium constant is:

For the reaction $cis-C_2H_2Cl_2 \rightleftharpoons trans-C_2H_2Cl_2$,the equilibrium constant at $500 \ K$ is $0.6$. The equilibrium constant for the reaction $trans-C_2H_2Cl_2 \rightleftharpoons cis-C_2H_2Cl_2$ at the same temperature will be ...............

For the reaction $:$
$CH_{4(g)} + 2O_{2(g)} \rightleftharpoons CO_{2(g)} + 2H_2O_{(l)},$
$\Delta H_r = -170.8 \ kJ \ mol^{-1},$ which of the following statements is not true $?$

If the equilibrium constant of the reaction $2HI \rightleftharpoons H_2 + I_2$ is $0.25$,then the equilibrium constant of the reaction $H_2 + I_2 \rightleftharpoons 2HI$ would be

In the reaction $A + 2B \rightleftharpoons 2C + D$,the initial concentration of $B$ was $1.5$ times that of $[A]$. At equilibrium,the concentrations of $A$ and $B$ became equal. The equilibrium constant for the reaction is: