True. The valid distributive law for ordinal multiplication is
The synthetic definition of ordinal multiplication takes a sequence of copies of the left factor, indexed by the right factor. A sequence indexed first by and then by is exactly the concatenation of the two corresponding sequences. Taking order types gives the identity. Equivalently, use transfinite induction on , with the successor rule and the supremum rule at limit ordinals.
False. Put and . Then
The two ordinals differ. The order of the factors matters in the distributive law for ordinal multiplication.