X, Y in the above conversion are respectively

Step-I . . .Reduction of -CHO to -CH2OH without reducing C = C∴NaBH4 is preferred; H2/cat not only reduces -CHO to -CH2OH but also reduces C = C to C - C.Step-II: Oxidation of -CH2OH to -CHO without oxidizing C = C∴PCC is preferred; KMnO4/H+ oxidizes -CH2OH to -COOH  and at the same time leads to oxidative cleavage of C = C