The maximum probability of finding an electron in the $d_{xy}$ orbital is

What is the maximum number of electrons that can have the quantum numbers $n = 5$ and $m_l = +2$?

Which of the following sets of quantum numbers is not possible for an electron?

In a chromium atom,the number of electrons which have $n = 2$ and $l = 1$ is:

Which of the following are correct?
$(1)$ Electron density in $XY$ plane for $d_{x^2-y^2}$ orbital is zero.
$(2)$ The energy of $3p$-orbital is higher than the energy of $2p$-orbital.
$(3)$ $3p_z$-orbital has one angular node.
$(4)$ $4f$-orbital has no radial node.

The total number of orbitals present for principal quantum number,$n=4$ is