Identify the product in the following reaction.

The product $(P)$ is:

Reaction of but$-2-$ene with acidic $KMnO_4$ gives:

$R_f$ value for $2$-methylpropene in a solvent system (Ethyl acetate + ether) is $0.42$. $2$-methylpropene is treated with dilute $H_2SO_4$ to give major organic product $(X)$. $R_f$ value for $(X)$ in the same solvent system under identical condition will be:

$X$ in the above reaction is

Which of the following compounds on heating with potassium permanganate $(KMnO_4)$ and dilute sulphuric acid $(H_2SO_4)$ forms adipic acid?