The final word is this:
A subset of Chabad Rabbonim are the only talmidei chachamim alive today who say that it’s possible for Moshiach to be a resurrected dead person. Literally every other frum Rov and Talmid Chacham says it’s not possible, and many say that it’s apikorsus to say so.
So that’s the final word. If you’re a follower of one of those Chabad Rabbis, gezunteh heit. Go and believe whatever you want to believe. But have in mind that the entire rest of the frum world looks at you like we look at Conservative Jews: Heart in the right place, but believes in things outside of Yiddishkeit.