Question

AB+CD>AD+CB or AB+CD>CB+AD
Which form is correct for Double displacement reaction?

Answer 1

 double displacement reaction is a type of reaction where two reactants exchange ions to form two new compounds. Double displacement reactions typically result in the formation of a product that is a precipitate.

Double displacement reactions take the form:
AB + CD → AD + CB

The reaction occurs most often between ionic compounds, although technically the bonds formed between the chemical species may be either ionic or covalent in nature. Acids or bases also participate in double displacement reactions. The bonds formed in the product compounds are the same type of bonds as seen in the reactant molecules. Usually, 

Answer 2

Hey your answer is here
both form is correct for Double Displacement Reaction

Because in Double Displacement Reaction
two products change their products with each other

and
in the above form both have double Displacement reaction

hope it was helpful for you