What is the difference in terms of molar masses of the second and fourth members of a homologous series?

Which of the following hydrocarbons has the lowest dipole moment?

What is the number of moles of $sp^3$ hybrid carbon atoms in one mole of $2-$Methylbut$-2-$ene?

Rank the following in the increasing order of rate of reaction with $HBr$.

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:

Identify product $(P)$