Which one of the following alkenes will react fastest with $H_2$ under catalytic hydrogenation condition?

Which of the following hydrocarbons has the lowest dipole moment?

What are $X$ and $Y$ respectively in the following sets of reactions?
$I. \ CH_3CH_2CH_2OH \xrightarrow{PBr_3} X$
$II. \ CH_3CH=CH_2 \xrightarrow{HBr, (C_6H_5COO)_2} Y \text{ (major)}$

The reaction is given by:
($1$-hydroxycyclopentane$-1,1-$dicarboxylic acid) $\xrightarrow[\Delta ]{K_2Cr_2O_7}\,(P)$
Product $(P)$ will be:

The octane number of a sample of petrol is $40$. It means that its knocking property is equal to the mixture of

The product of the following hydrogenation reaction is:
$C_6H_6 + H_2 \xrightarrow{\text{Catalyst, High temperature and pressure}} ?$
Given: $1 \text{ eqv. of } C_6H_6$ and $1 \text{ eqv. of } H_2$.