(For denominations who accept icons) Who is "Jesus Christ of the old days" icon?

I'm Eastern Orthodox, but this question can be answered by catholics and any denomination that accepts icons. I went today to my local church and I saw a painting on a wall that I never noticed. It was Jesus Christ, depicted as an old man with white hair and a white beard. The title of this painting roughly translates to "Jesus Christ, the One of the old days". I searched online when I returned home and didn't understand it very well. As far as I understand it is a depiction of God, The Son before He became a human being born from the Virgin Mary. Apparently, in the Orthodox world (it might be in the Catholic Church as well), there is a whole debate about the aspect of God The Father can and should be depicted in icons. Many say that The Father can't be drawn because of Exodus 33:20: "But,” He said, “you cannot see My Face, for no one may see me and live.”. Some say that the icon I mentioned earlier is actually God The Father, not Jesus Christ. I really don't understand what is all about, and why we need a version of Jesus Christ as an old man and a version of Jesus Christ as a young man. This icon raises some questions I always asked myself: - Where was Jesus Christ before His earthly birth? We know that the Trinity dogma states that The Son was born before eternity, so He pretty much existed forever and doesn't have a start. But 2000 years ago He became a human through the Virgin Mary. The question it begs is where and what did Jesus do from eternity to His earthly birth. Did He stay at the right side of The Father as He did after Ascension? - Why didn't He explicitly show Himself to the promised people? We, Christians often seem to believe that every time God showed Himself on the surface of the earth, as when He wrestled with Jacob, or when He came to Abraham at the Mamvri Tree, it was actually The Son, not The Father. But then why didn't Jesus in general show Himself explicitly to the Jews before? Why didn't Jesus tell Abraham or Moses explicitly: "I am Jesus, The Son of God, I am different than My Father, but I am also the same as My Father"? - When did the man Jesus on Earth realize He is The God Jesus that lived for eternity? The Baby knew He was Jesus, and knew His life in heaven before birth for eternity.
"Cel vechi" from the left side translates to "The Old" and "De zile" translates to "of days", and "IC XS", as you already know is the greek-byzantine acronym for Iesous Cristos(Ιησουσ Χριστοσ).