Which of the following is the correct electronic configuration?

$(a)$ How many sub-shells are associated with $n=4?$
$(b)$ How many electrons will be present in the sub-shells having $m_{s}$ value of $-1/2$ for $n=4?$

The portion of orbital diagrams representing the electronic configuration of certain elements is shown below. Which of them violate Pauli's Exclusion principle?

What is the number of radial nodes in the $2s$ orbital?

Which of the following statements are correct?
$(a)$ When an electron in an atom moves from $n=4$ to $n=2$,it gains energy.
$(b)$ An electron in a $3p$ orbital would have less energy than an electron in a $2p$ orbital.
$(c)$ $A$ $3s$ subshell has a maximum of $2$ electrons.
$(d)$ $A$ $3^{rd}$ orbit may contain a maximum of $10$ electrons.

What is the relationship between the shapes of $3d_{xy}$ and $3d_{x^2-y^2}$ orbitals?