Which of the following principles/rules limits the maximum number of electrons in an orbital to two?

Which two orbitals are located along the axes and not between the axes?

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.
Select the incorrect statements $:-$

The correct electronic configuration of $Ti$ $(Z = 22)$ atom is:

How many electrons can be fit into the orbitals that comprise the $3^{rd}$ quantum shell $(n = 3)$?

The total number of unpaired electrons in $d$-orbitals of atoms of element of atomic number $29$ is