Which of the following shows a linear structure?

Suggest reasons why the $B-F$ bond lengths in $BF_{3}$ $(130 \ pm)$ and $BF_{4}^{-}$ $(143 \ pm)$ differ.

Among the triatomic molecules/ions,$BeCl_2, N_3^{-}, N_2O, NO_2^{+}, O_3, SCl_2, ICl_2^{-}, I_3^{-}$ and $XeF_2$,the total number of linear molecule$(s)$/ion$(s)$ where the hybridization of the central atom does not have contribution from the $d$-orbital$(s)$ is
[Atomic number: $S=16, Cl=17, I=53$ and $Xe=54$ ]

In $SO_2$,$NO_2^-$ and $N_3^-$ the hybridizations at the central atom are respectively $:$

Which of the following species/ions has an octahedral geometry?

What are the requirements for the formation of hybrid orbitals?