The nature of hybridization in the $NH_3$ molecule is

The correct order of bond angle is:

What is meant by hybridisation? The compound $CH_2 = C = CH_2$ contains $sp$ and $sp^2$ hybridised carbon atoms. Will it be a planar molecule?

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

When $BCl_3$ is treated with water,it hydrolyses and forms $[B(OH)_4]^-$ only,whereas $AlCl_3$ in acidified aqueous solution forms $[Al(H_2O)_6]^{3+}$ ion. Explain what are the hybridizations of boron and aluminum in these species?

The formation of $PCl_3$ is explained on the basis of what hybridization of the phosphorus atom?