Chemistry question help please organic

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I could, but I think it would be more instructive to give a response for future readers.
If you were to convert the dibromoalkane into a diol (by hydrolysis) and then oxidise it to a dicarboxylic acid, you would make ethanedioic acid, since the dibromoalkane has a carbon chain that is only two carbons long - oxidation does not cause carbons to appear out of nowhere. As such, a method to expand the carbon chain must be employed.
The methods that would work are the Grignard reaction (addition of Mg in dry ether, followed by CO2 and then dilute HCl) and cyanation (nucleophilic substitution with KCN, followed by acidic hydrolysis). The former of these two methods is not expected by most exam boards at A level (in fact I believe only Edexcel requires it). As such, you are better off using the cyanation method unless you are doing Edexcel and are working with a halogenated arene substrate (i.e bromobenzene)