Mya88,
Yes, many religions are mentioned in connection with the underworld.
Christianity is as old as the earth, and nothing much has changed about its teachings since time immemorial.
I'd just like to clarify something you mentioned. Those who only look at Christianity past Anno Domini may not understand your statement. Historically, Christianity is "as old as the earth" although the name "Christian" only came up after Christ walked the paths of Palestine. However, God's eternal pre-existence and creatorship makes His people like Adam, Enoch, Job, Abraham, Isaac and Jacob to be Christian even though they did not meet the incarnate Christ. The Bible suggests that it was Christ who interacted with these pioneers (met Abraham by the trees of Mamre, met Moses in the burning bush, was with the three Hebrew boys in the fiery furnace etc).
Daniel 3
24 Then Nebuchadnezzar the king was astonished, and rose up in haste, and spake, and said unto his counsellors, Did not we cast three men bound into the midst of the fire? They answered and said unto the king, True, O king.
25 He answered and said, Lo, I see four men loose, walking in the midst of the fire, and they have no hurt; and the form of the fourth is like
the Son of God.John 11 In the beginning was the Word, and the Word was with God, and the Word was God.
2 The same was in the beginning with God.
3 All things were made by him; and without him was not any thing made that was made.
4 In him was life; and the life was the light of men.
http://egwtext.whiteestate.org/publication.php?pubtype=Book&bookCode=PP&lang=en&pagenumber=139"Two of the heavenly messengers departed,
leaving Abraham alone with Him whom he now knew to be the Son of God.