Oh, come now. What part of "if you pray to God, He will regenerate your amputated limb" don't you understand?
I don't understand what the word "God" refers to. [ETA]And "He??" What is that supposed to mean? Are we dealing with chromosomes, or penises, or just a bit of flowery language? (What if it turns out to be a "she" that made the limbs regrow, huh?

)[/ETA]
And, on top of that, I have been told that prayer does not work that way. *shrugs* Your requirements just strike me as utterly arbitrary.
That's no less understandable than "if you drop that glass, it will break." As a matter of fact, it might well be more understandable, since sometimes glasses don't break when dropped, but we're talking about a hypothetical where prayer always works.
As Yoink pointed out, we don't know why things fall; we just know that gravity exists and acts in a predictable way.
Well, we just call that what makes stuff fall, whatever it is exactly, "gravity." If it turns out to be a little ... uhmmm ... greener than expected, it'll still be "gravity." No problem.
What about "God?" Would it still be called "God" if it just turns out to be utterely boring. I have my doubts.
As I pointed out, we don't know why we feel pain; we just know that we do -- and we know that certain chemicals will reliably prevent us from having that feeling.
We call whatever it is exactly that we feel by the word "pain." Might have something to do with neurons and/or nerve thingies, or whatever, it'll be "pain" no matter what.
And that is the difference. Are we to call whatever it is exactly that makes limbs regrow after prayer by the word "God?" Does prayer actually work that way? Does "God?"
But I feel confident that the statement "glasses often break when dropped" has been proven.
And I think that we can ditch the truthfulness of the statement that "if you pray to God, He will regenerate your amputated limb." It'd be required that, at least once in a while, after having uttered some borderline arbitrary mumbo-jumbo something obtains that could be called "aputated limb regrowing."
Moreover there is the aforementioned point that many theists deny that prayer actually works in
any such petitive way (despite the fact that there are plenty of theists who do petitive prayer nevertheless). Or that "God" works in such a way.
I mean we could devise some test for glass, along the lines that if it is dropped, then limbs regrow. Or that we are dealing with gravity, if after having uttered a prayer glass breaks. In the same fashion you could make the statement that you are dealing with God, if, after having uttered some prayers, limbs regrow. Or that you are dealing with God, if, after having dropped a glass, the glass shatters.
Sure you could do all this. But it'd be arbitrary nevertheless.
And ... I have absolutely have no clue what I would have to mean were I to say "I believe in God." I could raise the mere requirement that if it is "necessary being" then by definition it is also "God" - no matter what it is exactly. Then what? Not magical enough?