Which rule describes the arrangement of electrons in subshells of the same energy?

The maximum number of electrons present in an orbital with $n=4, l=3$ is

The energy required to remove an electron from different subshells of a $H$ atom is given below. What is the order of these energies?

Consider the following statements:
$(a)$ Electron density in the $XY$ plane in $3d_{x^2-y^2}$ orbital is zero.
$(b)$ Electron density in the $XY$ plane in $3d_{z^2}$ orbital is zero.
$(c)$ $2s$ orbital has one nodal surface.
$(d)$ For $2p_z$ orbital,$YZ$ is the nodal plane.
Specify True or False.

Which of the following is/are not correct with respect to energy of atomic orbitals of hydrogen atom?
$A$. $1s < 2p < 3d < 4s$
$B$. $1s < 2s = 2p < 3s = 3p$
$C$. $1s < 2s < 2p < 3s < 3p$
$D$. $1s < 2s < 4s < 3d$
Choose the correct answer from the options given below:

Which of the following combinations of statements is true regarding the interpretation of atomic orbitals?
$1$. An electron in an orbital of high angular momentum stays further away from the nucleus than an electron in an orbital of lower angular momentum.
$2$. For a given value of the principal quantum number, the size of the orbit is inversely proportional to the azimuthal quantum number.
$3$. According to wave mechanics, the ground state angular momentum is equal to $\frac{h}{2\pi}$.
$4$. The plot of $\Psi$ vs $r$ for various azimuthal quantum numbers shows the peak shifting towards higher $r$ values.