What is blister copper?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The reduction of a metal oxide is easier if the metal formed is in liquid state than solid state.
Reason $R$: The value of $\Delta G^{\ominus}$ becomes more on negative side as entropy is higher in liquid state than solid state.
In the light of the above statements,choose the most appropriate answer from the options given below.

The purest form of iron is:

Cryolite $(Na_3AlF_6)$ helps in:

In the equation,the metal $M$ is:
$4M + 8CN^- + 2H_2O + O_2 \xrightarrow{} 4[M(CN)_2]^- + 4OH^-$

Which of the following compounds is used for the extraction of aluminum by electrolysis?