Increasing order of the nucleophilic substitution of following compounds

Which of the following hydrocarbons reacts easily with $\mathrm{MeMgBr}$ to give methane?

Adiabatic free expansion of ideal gas must be

An optically active alkene having molecular formula $\mathrm{C}_8 \mathrm{H}_{16}$ gives acetone as one of the products on ozonolysis. The structure of the alkene is