Maximum number of electrons possible with spin quantum number $+\frac{1}{2}$ with principal quantum number $n=4$ in an atom is

What is the maximum number of orbitals that can be identified with the following quantum numbers?
$n = 3, l = 1, m_l = 0$

Which of the following sets of quantum numbers is not valid?

All electrons in the $4p$ sub-shell must be characterized by which of the following quantum numbers?

The general configuration of the outermost and penultimate shell is $(n - 1)s^2 (n - 1)p^6 (n - 1)d^x ns^2$. If $n = 4$ and $x = 5$,then the number of protons in the nucleus will be:

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.