What is the shape of monoclinic sulphur?

$A$ piece of copper can displace metal from the solution of which of the following?

The following reaction takes place when aluminium powder is heated with $MnO_2$:
$3MnO_2(s) + 4Al(s) \rightarrow 3Mn(l) + 2Al_2O_3(l) + \text{Heat}$
$(a)$ Is aluminium getting reduced?
$(b)$ Is $MnO_2$ getting oxidised?

Which one of the following metals does not react with cold as well as hot water?

Which substance is used for the chemical reduction of metal oxides like chromium and manganese to obtain the metal?

Which medicine is prepared using ammonia?