After the $np$ orbital is completely filled,in which orbital does the next electron enter?

The correct set of quantum numbers for the unpaired electron of a chlorine atom is:

While filling up of electrons in the atomic orbitals,the $4s$ orbital is filled before the $3d$ orbital but reverse happens during the ionisation of the atom. Explain why?

If the value of the azimuthal quantum number $l$ is $2$,then the total possible values of the magnetic quantum number will be

The angular part of the wave function for an orbital is given by $\psi_{(\theta, \phi)} = \left( \frac{15}{4\pi} \right)^{1/2} \sin \theta \cos \theta \sin \phi$,where $\theta$ is the angle from the $z$-axis. The angular node$(s)$ are:

If the principal quantum number $n=6,$ the correct sequence of filling of electrons will be