It's more usual for the spare to be a "base" model size (i.e. steel) rather than the more expensive OEM alloy. Main point is the overall diameter rather than profile.I think any tire is fine as long as its profile/dimension is the same as the tire currently fitted to your Rio. Mine is 185/65 R15 (15-inch Kumho Solus).
RIOs that I've seen are 4-lug pattern. Highly unlikely that they've changed that for the new model.Rio Sedan
I was thinking factory donuts. I did not know if the 2nd generation donut would fit on the 3rd generation. I did not know if the lug pattern was the same or not.