There are neither demons nor devils in Merindrea, and never were. As much as a million years ago, a very human-like but pre-human race became geographically isolated, and their “devilish” features became pronounced. By the time migration brought them into contact with humans again they had diverged down a different evolutionary path. There is no compatibility between tieflings and humans or elves. They are a different species.
No one is surprised to see tieflings, and there is no supernatural overtone to their appearance (even in elvish religions there aren’t any malignant spirits as such). Humans look down on them much the same as they look down on elves, except that it’s much more common to see tieflings and humans working together than to see humans and elves.
Do not exist in Merindrea. To play one you’d have to be a unique import from another world, requiring a good roleplaying reason.
Do not exist in Merindrea. Could potentially be played as a special creation of the Forest Lord, although this would make you the natural enemy of most other playable races.
If one was in the world, it would be tied to the dead elvish gods somehow. In fact, a deva might be the husk of one of those gods. More or less a unique case.
Like dragonborn, they just don’t exist. The only way to play one would be an import from a foreign world.