Statement I : All S_N1 reactions involve racemization.

Statement II : All S_N2 reactions proceed with the formation of transition state.

(I) ${\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{Br}\underset{{\mathrm{S}}_{{\mathrm{N}}^1}}{\overset{{\mathrm{OH}}^{-}}{\to }}{\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{OH}$

No racemic mixture because the product has no chirality.

(II)  All S_N2 reactions proceed with the formation of transition state.