Addressing the OP only, Elijah has already come..... supportive scripture, The transfiguration of Christ, read Matthews chapter 17. this is where Moses and Elijah "appeared" unto our Lord Jesus the Christ. and coming down from the Mountain, the Lord Jesus disciples asked him a question, LISTEN CAREFULLY. Matthew 17:10 "And his disciples asked him, saying, Why then say the scribes that Elias must first come?" Matthew 17:11 "And Jesus answered and said unto them, Elias truly shall first come, and restore all things." Matthew 17:12 "But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them." Matthew 17:13 "Then the disciples understood that he spake unto them of John the Baptist."
John the Baptist is the Elijah, who has already come. he, John, is one of the two witness mention in Revelation 11.
now, listen to the Lord Jesus WHO CANNOT LIE, his testimony of John. supportive scripture, Matthew 11:7 "And as they departed, Jesus began to say unto the multitudes concerning John, What went ye out into the wilderness to see? A reed shaken with the wind?" Matthew 11:8 "But what went ye out for to see? A man clothed in soft raiment? behold, they that wear soft clothing are in kings' houses." Matthew 11:9 "But what went ye out for to see? A prophet? yea, I say unto you, and more than a prophet." Matthew 11:10 "For this is he, of whom it is written, Behold, I send my messenger before thy face, which shall prepare thy way before thee." Matthew 11:11 "Verily I say unto you, Among them that are born of women there hath not risen a greater than John the Baptist: notwithstanding he that is least in the kingdom of heaven is greater than he." Matthew 11:12 "And from the days of John the Baptist until now the kingdom of heaven suffereth violence, and the violent take it by force." Matthew 11:13 "For all the prophets and the law prophesied until John." Matthew 11:14 "And if ye will receive it, this is Elias, which was for to come." Matthew 11:15 "He that hath ears to hear, let him hear."
this is why his disciple understood, in Matthews 17, coming down from the mountain, that this Elias/Elijah is John the Baptist.
now, let's see it plainly. The conception of John the Baptist. Luke 1:5 "There was in the days of Herod, the king of Judaea, a certain priest named Zacharias, of the course of Abia: and his wife was of the daughters of Aaron, and her name was Elisabeth." Luke 1:6 "And they were both righteous before God, walking in all the commandments and ordinances of the Lord blameless." Luke 1:7 "And they had no child, because that Elisabeth was barren, and they both were now well stricken in years." Luke 1:8 "And it came to pass, that while he executed the priest's office before God in the order of his course," Luke 1:9 "According to the custom of the priest's office, his lot was to burn incense when he went into the temple of the Lord." Luke 1:10 "And the whole multitude of the people were praying without at the time of incense." Luke 1:11 "And there appeared unto him an angel of the Lord standing on the right side of the altar of incense." Luke 1:12 "And when Zacharias saw him, he was troubled, and fear fell upon him." Luke 1:13 "But the angel said unto him, Fear not, Zacharias: for thy prayer is heard; and thy wife Elisabeth shall bear thee a son, and thou shalt call his name John." Luke 1:14 "And thou shalt have joy and gladness; and many shall rejoice at his birth." Luke 1:15 "For he shall be great in the sight of the Lord, and shall drink neither wine nor strong drink; and he shall be filled with the Holy Ghost, even from his mother's womb." Luke 1:16 "And many of the children of Israel shall he turn to the Lord their God." Luke 1:17 "And he shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord." (READ THAT VERSE AGAIN). Luke 1:18 "And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years." Luke 1:19 "And the angel answering said unto him, I am Gabriel, that stand in the presence of God; and am sent to speak unto thee, and to shew thee these glad tidings."
John the Baptist was in the spirit and power of Elias WHICH WAS TO COME. so if anyone is still waiting for the flesh and blood man, the prophet Elijah, you will be waiting a very long time. HE HAS ALREADY COME. as the Lord Jesus said, "He that hath ears to hear, let him hear."
the Lord Jesus, God himself told us and his angel Gabriel has told us that Elijah has already come in spirit and power.
101G.