Ways to change the spontaneity of a reaction I can think of any other way to influence the value of $\Delta G$ than (1) change the temperature (2) providing an external source to overcome the negative cell potential

The relationship between $\Delta G$ and $E_{\mathrm{cell}}$ is $\Delta G =-nFE_{\mathrm{cell}}$

Between $\Delta H$, $\Delta S$ and $\Delta G$ is $\Delta G=\Delta H - T\Delta S$

Sometimes, temperature won't do anything to change the spontaneity. But if we change $\Delta G$ through $\Delta E_{\mathrm{cell}}$ by providing external voltage in excess of the negative voltage, and though $\Delta G$ we are also able to influence enthalpy and entropy(???).

This is the part I am not sure about. Besides the title question, a sub-question is: how in this way can we change the enthalpy and entropy?
Natural variables of $\Delta G$ are $p$, $T$, and $N_i$.

$p$ = pressure

$T$ = Temperature

$N_i$ = number of particles  (or number of moles)

The derivation showing this is listed on the Wikipedia.