“I have 1 simple question for Lubavitch Chassidim. If Moshiach comes today but he isn’t the Rebbe, would you accept him?
I would prefer a straight Yes or No answers.“
That’s like asking if a chazir chews its cud would you eat it
If Lubavitch claims “the rebbe IS moshiach” there is no other option and if there is then their belief isn’t ironclad then your “hypothetical scenario” would be incongruent