Why is it possible to use melting point to distinguish the different stereochemistry of the
products? (Hint: what is the relationship of the different stereoisomers of the product?)
I don't know about the hint but cis-trans isomers have different melting and boiling points. Here is a page that explains that and gives an example. The example is down about 3/4 of the page.
http://www.chemguide.co.uk/basicorg/isomerism/geometric.html