Why ef and not (f)e/(f)o?
Al three should be accepted.
But is 'ef' correct? Like is it something used in specific places or...?
Ef (from what I know) is quite formal, since I've only seen it used to refer to God. But it could be a common word in another dialect.
Is "e'n" a contraction of "ef yn" then? I don't remember seeing that in any lesson notes.
"e'n" is more likely to be a contracted form of "fe'n" where the "f" has been dropped as opposed to "ef".