No. They are not the same.
St John the Apostle was a former fisherman who was called to be one of the twelve disciples whom Jesus taught and trained during his ministry here on earth (Luke 5:1-11). John the Baptist was Jesus' cousin, born to Elizabeth and Zacharias (Luke 1:1-80; 3:1-18) who preached repentance to the Jews prior to Jesus' earthly ministry. John the Baptist is also call the "forerunner" of Christ because of his ministry to prepare others to receive Jesus' message of salvation.
No.
Yes. they are different ways of descibing the same person.
No. John the Baptist did not write any books in the New Testament.
Elizabeth is the mother of John. Salome is the one that had John killed.
No.
No.
No.
The name St. Elizabeth usually refers to the mother of John the Baptist who is a different person from Elizabeth of Hungary.
John the Baptist.
No, he wasn't. It was his son who ordered the death of the John the Baptist.
About the same.
Zacharias was a Levite and was not related to Jesus, who was from the tribe of Judah. Jesus and John the Baptist were related through Zacharia's wife, Elizabeth and Mary, Jesus' mother.