In essence what BB1987 is the best dividing line, though I guess that "actually completed and ready to fly, even if never flown" would be also acceptable, considering that it "really existed" (as completed aircraft).
Btw. the Ho-229
did flew - unpowered glider (designated as Ho.IX V1) in March 1944 and powered Ho.IX V2 in February 1945. Of course, certain designation subtleties (first two prototypes were usually called Ho.IX while third and next prototypes were to be called Ho.229 but also slightly larger) may encourage discussion about applicaplibity of either name, but "simply speaking" I'd say it was
very real life.