The alkene $C_6H_{10}$ producing $OHC-(CH_2)_4-CHO$ on ozonolysis is

Upon heating with acidic $KMnO_4$,an organic compound produces hexan$-1,6-$dioic acid as the major product. The starting compound is

The major product $(A)$ is:

Write in brief about the preparation of alkene from vicinal dihalide.

$A$ gas decolourises Bayer's reagent but does not react with Tollen's reagent. This gas is:

$(CH_3)_2C=C(CH_3)_2 \xrightarrow{\text{Catalyst}, H_2} \text{Number of optical isomers in the product?}$