To solve this problem, we need to understand the ozonolysis reaction of alkenes.$\\$Ozonolysis of an alkene involves the cleavage of the double bond, resulting in the formation of carbonyl compounds.$\\$Given that methanal (formaldehyde, $$HCHO$)$ is one of the products, the alkene must have a terminal $\\$double bond with at least one hydrogen atom attached to the carbon involved in the double bond.$\\$Let's analyze the options:$\\$Option 1:$\\$The structure is a cyclohexene derivative with a propyl group. The double bond is not terminal,$\\$so it cannot produce methanal.$\\$Option 2:$\\$The structure is a cyclohexene derivative with a vinyl group ($$CH$_2$=CH$_2). \\$The double bond is terminal, and ozonolysis will cleave it to form methanal and another carbonyl compound.$\\$Option 3:$\\$The structure is a cyclohexene derivative with a propyl group. The double bond is not terminal,$\\$so it cannot produce methanal.$\\$Option 4:$\\$The structure is a cyclohexene derivative with a propenyl group. The double bond is not terminal,$\\$so it cannot produce methanal.$\\$Therefore, the correct option is Option 2, where the alkene has a terminal double bond capable of forming methanal upon ozonolysis.