Which of the following does **$NOT$** liberate $H_2$ gas on reaction with $Na$ metal?

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

$A$ hydrocarbon $C_5H_8$ consumes two moles of hydrogen. On ozonolysis,it produces $2-$oxopropanal and methanal. The hydrocarbon is:

The correct order of heats of combustion of the following compounds is:
$(I)$ Cyclopropane
$(II)$ Cyclobutane
$(III)$ Cyclopentane

Styrene on reaction with reagent $X$ gave $Y$, which on hydrolysis followed by oxidation gave $Z$. $Z$ gives a positive $2,4-DNP$ test but does not give the iodoform test. What are $X$ and $Z$ respectively?

Answer the following questions:
$(i)$ What is the bond length of $C-C$,$C=C$,and $C\equiv C$?
$(ii)$ What will be the effect on bond length as bond multiplicity increases?
$(iii)$ What is the relation between reactivity of compound,bond strength and bond order between two carbon atoms?
$(iv)$ What is the rate of reaction of $Cl_2, Br_2,$ and $I_2$ with $CH_2=CH_2$?
$(v)$ What is the difference between $2-$butyne and $1-$butyne? By which test can we distinguish between these two?
$(vi)$ Which real product is obtained on hydrolysis of alkyne? Why?
$(vii)$ Give the structure and $IUPAC$ name:
$(a)$ Vinyl chloride
$(b)$ Vinyl cyanide
$(c)$ Glyoxal
$(d)$ Silver acetylide
$(e)$ Diacetyl
$(f)$ Glycol