This story essentially takes place at the same time as The Christmas Invasion, with the Third Doctor arriving in Jackie's flat after the Tenth Doctor's TARDIS has been taken up to the Sycorax ship and leaving after his future self has been returned to London.
Jackie believes that the Doctor has regenerated again , and, when meeting Jo and Yates, she thinks that Rose and Mickey have also changed their appearance. (TV: The Christmas Invasion)
According to one account, the Master had the appearance of Roger Delgado while on Gallifrey. According to another, he had Anthony Ainley's likeness. According to another one, the one with James Dreyfus's appearance was the incarnation who ran away from Gallifrey.
While fighting to extend his life at the end of his regeneration cycle, many bodies were possessed by the Beevers incarnation, but all kept somehow reverting to his real being until he finally regenerated into the MacQueen one. Hence, these sections cannot be strictly chronological
