For a reaction $\Delta H = -30 \ kJ$ and $\Delta S = -45 \ J \ K^{-1}$,at what temperature does the reaction change from spontaneous to non-spontaneous (in $K$)?

The condition of spontaneity of a process is

For the decomposition reaction of $N_2O_4$,$\Delta H = 58.04 \, kJ$ and $\Delta S = 176.7 \, J/K$. Calculate $\Delta G$ in $kJ$ at $T = 298 \, K$.

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)

In the conversion of limestone to lime,$CaCO_{3(s)} \rightarrow CaO_{(s)} + CO_{2(g)}$,the values of $\Delta H^{\circ}$ and $\Delta S^{\circ}$ are $+179.1 \ kJ \ mol^{-1}$ and $160.2 \ J \ K^{-1} \ mol^{-1}$ respectively at $298 \ K$ and $1 \ bar$. Assuming that $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not change with temperature,the temperature above which the conversion of limestone to lime will be spontaneous is ........... $K$.

Which of the following formulas is correct for Gibbs free energy $(G)$?