Does Luke 9:62 describe backsliders as though they were never saved?

I recently heard it taught that Luke was a gentile and I am having a hard time believing this. My question is was Luke a gentile?

In Mark 9:11-13 we read about the prophecy of Elias. Verse 13 says "as it is written of him". Now, where is it written?

Why did Jesus tell Mary not to touch Him since he had not ascended? When did he ascend? Did not he invite Thomas to thrust his hand in his side? Also when did Jesus present the blood to the Father? Was it the literal blood that came from his body on the cross?

What does Matthew 16:28 mean? What did Jesus mean when He said "Verily I say unto you, There be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom."?

Please explain Matthew 11:12. Some people say that this is referring to heaven while others say that it refers to the believers on earth.

In Matthew 2:23 it says "that it might be fulfilled which was spoken by the prophets, He shall be called a Nazarene." I have looked quite thoroughly for this verse in the prophets but cannot find it. Can you help with this?

I've been reading the Bible and it says in Matthew that Jesus had 4 brothers and it mentions he had sisters, but it doesn't give their names or how many. I was wondering if you knew what happened to his brothers and sisters and what the sister's names were?

What are the two mountains of brass? What would be the north country and south country?

In Ezekiel, chapters 40-47, is this a future setup of what has to happen with Israel as nation in the future? What is the period?