Which one is a wrong statement?

According to Hund’s rule, unpaired electrons in degenarate orbitals must have same spin quantum number.
Nitrogen electronic confi juration 

(1) Orbital angular momentum of electron
$=ħ\sqrt{\mathrm{I}(\mathrm{I}+\mathrm{l})},\left(ħ=\frac{\mathrm{h}}{2\pi }\right)\text{. }$
Since for s-orbital, l=0, total orbital angular momentum of electron in s-orbital is equal to zero.
(2) An orbital is designated by three quantum numbers n, l, and m. An electron in an atom is designated by n,
l, m, and s quantum numbers. 
(4) The value of m for d_z² is zero because it is oriented along 90^o with respect to the axis (cos 90^o=0).