>>33337498I am well aware the Retrogade is incredibly convoluted, but it's an interesting prospect. Now to answer your questions.
For the first ???, Outrage would still have no effect on Sylveon as that is how the Fairy-Typing operated, the move/ability won't change types if there was no type change beforehand (ergo Sylveon remains a Fairy-Type as Sylveon was always a Fairy-Type).
For the second ???, Shadow Ball would again have no effect as in Gen I Psychic was immune to Ghost-Type.
For the third ???, Bite would have no effect as Bite would become a normal type move and only have a 10% flinch chance, so Hydreigon would no longer get STAB (however if a move that was always Dark-Type was used, like Crunch, it would remain a Dark-Type and Hydreigon would get STAB on it).
And for the fourth ???, for all cases where the move originally affected the SPECIAL stat in Gen I, it will apply to both the Special Attack and Special Defense stats, so oldtimey would raise both Special Attack and Special Defense by two stages.