Which flux is used to remove $SiO_2$ impurity?

Among the following,an example of the thermite process is:

Which of the following is electrolyzed for the extraction of aluminum?

Which one of the following electrolytes is used in Down's process for the extraction of sodium metal?

Which one of the following is a wrong statement about cast iron?

The cyanide process of gold extraction involves leaching out gold from its ore with $CN^{-}$ in the presence of $Q$ in water to form $R$. Subsequently,$R$ is treated with $T$ to obtain $Au$ and $Z$. Choose the correct option$(s)$.
$1$. $T$ is $Zn$
$2$. $R$ is $[Au(CN)_2]^-$
$3$. $Z$ is $[Zn(CN)_4]^{2-}$
$4$. $Q$ is $O_2$