Yes, Christ is a title for Jesus but Jesus is not the only man who ever brought the Christ Spirit.
No, Christ is not a title for Baha'u'llah, but Baha'u'llah brought the Christ Spirit.
Jesus never promised to return to earth in the same body, He promised to send the Christ Spirit who He referred to as the Comforter and the Spirit of Truth. The Bible prophecies did not fail because the Comforter/Spirit of truth did come, in the person of Baha'u'llah.
John 14:16 And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever;
John 14:17 Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
John 14:26 But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.
John 15:26 But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:
John 16:7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
John 16:12-13 I have yet many things to say unto you, but ye cannot bear them now. Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.