Stamped concrete is dangerously slippery
That's a tricky one. Wax? It's supposed to be sealed but not with wax. If you can't identify exactly what it's composition is you'll have to resort to trial and error. Test removal methods in small inconspicuous areas. It may be extremely hard to remove the finish in winter. I would start with gentle solvents and progress up to etchants (acid that will actually eat a fine layer of concrete. Aggressive treatment will change the look of the concrete and will need to be resealed in the appropriate weather conditions. I would use salt and sand for the remainder of the winter and address it in the spring.