They can tell by whether or not you rebuild the Temple and bring world peace, etc. It’s not a birth right. It’s confirmed by achievement. It’s kind of like if there’s a prophecy that a guy will cure cancer. You’re not The Guy Who Will Cure Cancer until you cure cancer.
That’s correct. Without patrilinear descent from David, you can’t be the Messiah. That does make Matthew’s and Luke’s attempts to go through Joseph immaterial (and it can’t be passed through adoption either, which is another common apologetic).
That actually IS the literal claim in the Gospels. Matthew claims that Mary was literally knocked up by the Holy Ghost. It’s made clear that Joseph is not the biological father, because Joesph initially assumes she cheated on him and wants to divorce her.
Adoption doesn’t count. It has to be a blood descendant of David.
Technically, you’re not The Guy Who Will Cure Cancer after you cure cancer either.
I’m confused. Would the messiah know he’s the messiah or is he nominated?
He wouldn’t necessarily know he was the messiah (though he might know or think it). The question (for those Jews who believe in an actual human messiah) is whether he does all of the things the Bible says the messiah will do.
Once that happens, people will presumably turn around and say: “Holy cow, that dude’s the messiah.”
Thanks. That’s what I thought.
Isn’t that what Hindus would say when their Messiah arrives. 
According to Fr. Schneider who taught religion class at my High School, he did not.
I would not call a Jesuit uneducated or mistaken.