Michael B. Jordan says directing ‘Creed III’ has been the most “challenging” test of his career so far. The 35-year-old actor has appeared in almost 20 films since making his motion picture debut as a teenager more than 20 years ago but has now stepped behind the camera for the boxing sequel – which is a spin-off of the ‘Rocky’ franchise created by Sylvester Stallone – and was “pushing his limits” throughout the process even though he had a “clear vision” for what he wanted on screen. Jordan – who stars as heavyweight champion boxer Adonis Creed in the franchise – said: “My experience being on…