What is the value of $\Delta G$ for a water system in an environment at a temperature of $100 \ K$?

The standard state Gibbs free energies of formation of $C$ (graphite) and $C$ (diamond) at $T = 298 \ K$ are:
$\Delta_f G^0[C(\text{graphite})] = 0 \ kJ \ mol^{-1}$
$\Delta_f G^0[C(\text{diamond})] = 2.9 \ kJ \ mol^{-1}$
The standard state means that the pressure should be $1 \ bar$,and the substance should be pure at a given temperature. The conversion of graphite [$C$ (graphite)] to diamond [$C$ (diamond)] reduces its volume by $2 \times 10^{-6} \ m^3 \ mol^{-1}$. If $C$ (graphite) is converted to $C$ (diamond) isothermally at $T = 298 \ K$,the pressure at which $C$ (graphite) is in equilibrium with $C$ (diamond) is:
[Useful information: $1 \ J = 1 \ kg \ m^2 \ s^{-2} ; 1 \ Pa = 1 \ kg \ m^{-1} \ s^{-2} ; 1 \ bar = 10^5 \ Pa$ ] (in $bar$)

Under what conditions does a reaction always occur spontaneously?

For the reaction $Ag_2O_{(s)} \rightarrow 2Ag_{(s)} + 1/2 O_{2_{(g)}}$,the value of $\Delta H = 30.56 \, kJ \, mol^{-1}$ and $\Delta S = 66 \, J \, K^{-1} \, mol^{-1}$. At what temperature $(K)$ will the change in free energy for the reaction be zero?

Gibbs free energy $(G)$ is defined as

In all spontaneous processes,which of the following is true?