Isotopes of the alternative monster and the Skosyrsky algebra

We prove that the isotopes of the alternative monster and the Skosyrsky algebra satisfy the identity $\prod^4_{i=1}[x_i,y_i]=0$. Hence, the algebras themselves satisfy the identity $\prod^4_{i=1}(c,x_i,y_i)=0$. We also show that none of the identities $\prod^n_{i=1}(c,x_i,y_i)=0$ holds in all commutative alternative nil-algebras of index 3. Thus, we refute the Grishkov–Shestakov hypothesis about the structure of the free finitely generated commutative alternative nil-algebras of index 3.