For a spherical shell,which of the following statements is correct?

$12 \mu C$ and $6 \mu C$ charges are given to two conducting plates having the same cross-sectional area and placed face to face close to each other as shown in the figure. The resulting charge distribution in $\mu C$ on surfaces $A, B, C$ and $D$ are respectively,

$(a)$ $A$ conductor $A$ with a cavity as shown in Figure $(a)$ is given a charge $Q$. Show that the entire charge must appear on the outer surface of the conductor.
$(b)$ Another conductor $B$ with charge $q$ is inserted into the cavity keeping $B$ insulated from $A$. Show that the total charge on the outside surface of $A$ is $Q+q$ [Figure $(b)$].
$(c)$ $A$ sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.

Inside a charged hollow sphere,at any point the electric field $(E)$ and potential $(V)$ are

An empty thick conducting shell of inner radius $a$ and outer radius $b$ is shown in the figure. If it is observed that the inner face of the shell carries a uniform charge density $-\sigma$ and the outer surface carries a uniform charge density $\sigma'$,if the outer surface of the shell is earthed,then identify the correct statement$(s)$.

$A$ spherical conductor of radius $2 \, m$ is charged to a potential of $120 \, V$. It is now placed inside another hollow spherical conductor of radius $6 \, m$. Calculate the potential to which the bigger sphere would be raised. (in $, V$)