Reaction of $HBr$ with propene in the presence of peroxide gives

The product of the following reaction is: $CH_3-C(CH_3)_2-CH=CH_2 \xrightarrow[(ii) NaBH_4]{(i) Hg(OAc)_2, H_2O}$

The product $(A)$ is:

$A$ single compound of the structure $CH_3-CO-CH_2-CH_2-CH_2-CHO$ is obtainable from the ozonolysis of which of the following cyclic compounds?

Identify the product of ozonolysis of $but-2-ene$ from the following:

$Br-CH_2-CH=CH-CH_2-Br \xrightarrow{Zn (dust)} (A)$
Above reaction is an example of $1,4$-elimination. Predict the product.