Atoms that are ${\mathrm{sp}}^2$ hybridized form how many $\pi$ bonds?

Given the molecule $C_2{H}_4$ (ethene), label the hybridization of each carbon atom.

In the following carbon skeleton structure, which carbon atom(s) exhibit ${\mathrm{sp}}^2$ hybridization? (Assume the structure is ${\mathrm{CH}}_2$=${\mathrm{CH}}_1$-${\mathrm{CH}}_2$-${\mathrm{CH}}_3$)

After ${\mathrm{sp}}^3$ hybridization, the carbon atom has:

Which of the following atoms in histrionicotoxin 283a are ${\mathrm{sp}}^2$-hybridized?