When I want to ask whether or not something I have is what I think it is, I can't figure out exactly what to say.

これは梅じゃないの? (Rising intonation)

Is this not a plum?

これは梅じゃないね。(Falling intonation)

This isn't a plum, right?

How could I say something like

"This isn't a plum?!" (With a sense of surprise)

"Isn't this a plum?"

I'm not sure if I'm overthinking, but to me all these phrases mean something slightly different in English.