Which oxide of manganese is amphoteric in nature?

Given below are some statements about $Mn$ and $Mn_2O_7$. Identify the correct statements:
$A$. $Mn$ forms the oxide $Mn_2O_7$ in which $Mn$ is in its highest oxidation state.
$B$. Oxygen stabilizes the $Mn$ in higher oxidation states by forming multiple bonds with $Mn$.
$C$. $Mn_2O_7$ is an ionic oxide.
$D$. The structure of $Mn_2O_7$ consists of one bridged oxygen.
Choose the correct answer from the options given below:

Mention the type of compounds formed when small atoms like $H$,$C$ and $N$ get trapped inside the crystal lattice of transition metals. Also,give the physical and chemical characteristics of these compounds.

Ferric sulphate on heating gives:

$KMnO_4$ is the oxo-salt of the acid of which of the following oxides?

$A$ hard and resistant metal alloy generally used in the tip of the nib of a fountain pen is