Under what conditions does a reaction always occur spontaneously?

The occurrence of a reaction is impossible if

For a chemical reaction $A^{+} + B \rightleftharpoons C^{+} + D$ $(\Delta_{r} H^{0} = 80 \, kJ \, mol^{-1})$,the entropy change $\Delta_{r} S^{0}$ depends on the temperature $T$ (in $K$) as $\Delta_{r} S^{0} = 2T \, J \, K^{-1} \, mol^{-1}$.
Minimum temperature at which it will become spontaneous is ..... $K$. (Integer)

For a certain reaction, $\Delta H^{\circ} = 40 \text{ kJ}$ and $\Delta S^{\circ} = 80 \text{ JK}^{-1}$. Find the temperature at which $\Delta G^{\circ} = 0$. (in $\text{ K}$)

Spontaneity of a chemical reaction is decided by the negative change in

$A$ minus sign of the free energy change denotes that