The dibromo compound $[P]$ (molecular formula : $C_{9}H_{10}Br_{2}$) when heated with excess sodamide followed by treatment with dilute $HCl$ gives $[Q]$. On warming $[Q]$ with mercuric sulphate and dilute sulphuric acid yields $[R]$ which gives positive Iodoform test but negative Tollen's test. The compound $[P]$ is:

Which one of the following dienes would you expect to be the most stable?

Arrange the following in the correct order of their acidic strength:

$I. H_2C=CH_2$

$II. CH \equiv CH$

$III. CH_3-C \equiv CH$

$IV. CH_3-CH_3$

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

Identify the correct order of heat of hydrogenation.

$A$ molecule $P$ on treatment with acid undergoes rearrangement and gives $Q$. $Q$ on ozonolysis followed by reflux under alkaline condition gives $R$. The structure of $R$ is given below:
[Image of $R$]
The structure of $P$ is