Which of the following molecules does not obey octet rule?

Which of the following on reaction with Grignards reagent followed by hydrolysis forms tertiary alcohol?

In an ionic solid anions are arranged in hcp array and cations occupy $\frac{2}{3}$ of octahedral voids.

What is the formula of ionic compound? [consider $\mathrm{A}=$ cation; $\mathrm{B}=$ anion]

For a certain reaction $\Delta \mathrm{H}=-225 \mathrm{~kJ}$ and $\Delta S=-150 \mathrm{JK}^{-1}$. Find the temperature so that $\Delta G$ is zero.