Based on which rule is $2$-butene obtained as the major product from the dehydration of $2$-butanol?

Glycerol is a trihydric alcohol. It contains . . . . . .

$A \xrightarrow{KOBr} CHBr_3$
Here $A$ is:

Optically active $3-$methylpent$-1-$en$-3-$ol loses its optical activity after standing in water containing a few drops of acid,mainly due to the formation of:

An alcohol $X$ $(C_5H_{12}O)$ on dehydration gives $Y$ (major product). Reaction of $Y$ with $HBr$ gave $Z$ ($C_5H_{11}Br$,major product). $Z$ undergoes nucleophilic substitution in two steps. What are $X$ and $Y$?

Which reagent is required to convert cyclohexanol to cyclohexanone?