Did Jesus ever make an appearance before His human birth?

In the hours leading up to Jesus' birth (when Mary was in labor), a bright, large star appeared in the sky and shone gloriously, causing animals (sheep, cattle) and shepherds to look and be amazed. Not really an appearance from Jesus pre-birth himself but his birth was being announced and God's genes were coming down to earth to be put into Jesus.

The second Person of the Most Holy Trinity did of course exist from all eternity, but not as Jesus. Jesus didn't exist until the moment He was conceived in the womb of His mother Mary. 

Yes, there are several instances in the Old Testament. They are referred to a "Christophanies." 

Not according to canon.  But that may of course be retconned at any time.

The Bible teaches that Jesus Christ is Jehovah incarnate, the creation and begotten son of God.  Adam saw Jesus Christ.  Moses saw Jesus Christ.  The brother of Jared saw Jesus Christ.

There is some evidence that we're talking about Jesus in the early New testament when were discussing this king called Melchizedek.  The prince of Salem Jesus is also the Prince of Peace. Another word for Prince of Salem.

You might want to read the description in the Bible of this Melchizedek. Some say that he was an earthly manifestation of God or Jesus Christ

NO HE DID NOT....

The pre-incarnate Christ did make appearances in the OT.

Yes.  Moses saw him on Mt. Sinai, and he was in the furnace with Shadrach, Meshach and Abednego.

IDK, but maybe with Shadrach, Meshach and Abednego in the fiery furnace; they said there was a fourth with them who looked like the Son of God.  But that may have meant an angel.