Answers to your Questions
1. Why are the 2 genealogies for Jesus different in the Gospels?
You are referring to the genealogies listed in Matthew 1 and Luke 3. Matthew’s lineage is that of Jesus as king, which is the thrust of the whole gospel of Matthew. And the lineage of a king begins at the source of his dynasty and ends with himself. It is the regal legal line (“The throne of his father David”).
Luke’s lineage is that of the perfect Man, which is the thrust of the whole gospel of Luke. The lineage of the ideal man begins from his father, and goes backward as far as may be needed to justify the ideal. It is the natural legal line (“the seed of the Woman”). Matthew’s lineage is the lineage of Joseph, the earthly father. Luke’s lineage is the lineage of Mary, His mother; and although it begins with Joseph, he was the legal son of Heli through marriage to his daughter Mary.
2. What's the deal about baptizing for the dead?
Do people think that the dead can get into heaven if someone is baptized in their behalf?
The reference is 1 Corinthians 15:29: “Else what shall they do which are baptized for the dead, if the dead rise not at all? Why are they then baptized for the dead?” The argument in this passage is what is the use of being baptized, if it is only to remain dead? In other words, if Christ be not risen from the dead, then we cannot enjoy resurrection, and are therefore dead (spiritually). So why be baptized as a dead person, if there is no hope of resurrection of the dead.
The teaching in Romans is that we are buried by baptism to rise in a new, resurrected life, like Jesus coming forth from the tomb. However, if he didn’t come forth, then baptism is of no value. So why do it? There is no suggestion in this passage (by following the content) of vicarious baptism for those already physically dead. This teaching sprang up among the Marconites, lead by Marcion of Sinope around 144 AD; and again among the Mormons of today, a cult founded by Joseph Smith in the 1800s.