What is the role of limestone during the extraction of iron from haematite ore?

Which technique is used in the manufacture of aluminium from bauxite?

Consider the following reactions of metallurgy:
Ore '$X$' $\xrightarrow{\text{Roasting}}$ '$Y$' + $SO_2$ $\uparrow$
Ore '$Z$' $\xrightarrow{\text{Calcination}}$ '$Y$' + $CO_2$ $\uparrow$
'$Y$' + $C$ $\xrightarrow{1673 \ K}$ '$A$' (vapour) + '$B$' $(g)$
where '$A$' and '$B$' are respectively:

What is the slag formed in the extraction of iron?

Is it true that under certain conditions,$Mg$ can reduce $Al_2O_3$ and $Al$ can reduce $MgO$? What are those conditions?

Which of the following is obtained as a slag during the extraction of iron from iron oxide?