Assuming Z-axis as inter nuclear axis, which of the following statement is  not correct ?

‘sp²’ hybrid orbitals are oriented 120⁰ to each other 

‘sp’ hybrid orbitals are formed by the overlap of ‘s’ orbital and p_z orbital

d - orbital involved in sp³d hybridization is ${\mathrm{d}}_{{\mathrm{x}}^2-{\mathrm{y}}^2}$

In ${\mathrm{NH}}_4^{+}$, hybridization of ‘N’ atom is sp³