(a) Cyclohexanol is less acidic as compared to phenol because phenol is an aromatic compound while cyclohexanol is cyclic ring structure containing hydroxyl ion (-OH group).
In phenol benzene ring is having double bond and shows ${\mathit{s}\mathit{p}}^2$ hybridization. Because of more $\mathit{s}$-character it is more acidic.
(b) When phenol react with Ferric Chloride, it gives violet colour but cyclohexanol remains colourless when react with ${\mathit{F}\mathit{e}\mathit{C}\mathit{l}}_3$.