Jesus In The Old Testament?

I have read of several places in the Old Testament where Jesus appears on the scene.  First in creation with God, when God said: 1:26 Then God said, “Let us make mankind in our image, in our likeness, so that they may rule over the fish in the sea and the birds in the sky, over the livestock and all the wild animals, and over all the creatures that move along the ground.”

Also in the furnace with Shadrach, Meshach, and Abednego.  Who was that forth person? 
Daniel 3:24-26: 24 Then King Nebuchadnezzar leaped to his feet in amazement and asked his advisers, “Weren’t there three men that we tied up and threw into the fire?”

They replied, “Certainly, Your Majesty.”

25 He said, “Look! I see four men walking around in the fire, unbound and unharmed, and the fourth looks like a son of the gods.”

And how about that guy Joshua spoke with at Jericho?  Joshua bows down to him.  I dont think it could be an angel, since angels dont allow people to bow down to them (since they didnt let John bow to them in Revelation).
Joshua 5:13-15:  13 Now when Joshua was near Jericho, he looked up and saw a man standing in front of him with a drawn sword in his hand. Joshua went up to him and asked, “Are you for us or for our enemies?”

14 “Neither,” he replied, “but as commander of the army of the Lord I have now come.” Then Joshua fell facedown to the ground in reverence, and asked him, “What message does my Lord have for his servant?”

15 The commander of the Lord’s army replied, “Take off your sandals, for the place where you are standing is holy.” And Joshua did so.

What about Abraham?  Didnt he see Jesus?  Genesis 15:1-5  The Lord appeared to Abraham near the great trees of Mamre while he was sitting at the entrance to his tent in the heat of the day. 2 Abraham looked up and saw three menstanding nearby. When he saw them, he hurried from the entrance of his tent to meet them and bowed low to the ground.

3 He said, “If I have found favor in your eyes, my lord,[a] do not pass your servant by. 4 Let a little water be brought, and then you may all wash your feet and rest under this tree. 5 Let me get you something to eat, so you can be refreshed and then go on your way—now that you have come to your servant.”

“Very well,” they answered, “do as you say.”

Again, Abraham bows down to "the Lord", which he obviously saw in verse 1.