The key to both of your questions lies in the meaning of the word “synoptic.” It comes from the Greek word SYNOPTICUS which means “together seen.” It is a well-known fact that the Gospels of Matthew, Mark and Luke are very similar in their accounts of the life, ministry, death, and resurrection of Christ. In other words, they have a COMMON VIEW. For example, many of the same miracles performed by Jesus and the parables that He taught are in all three gospels. The Gospel of John stands out from them for the Apostle John omits many of the miracles found in the Synoptic Gospels and John was not inspired to write of any of the parables told by the Lord Jesus. Instead of concentrating so much on Christ’s birth and earthly ministry, John focuses on Him as the eternal Word, the only begotten Son Who was sent of the Father to die on the cross to provide salvation for lost and guilty sinners. The following verses illustrate this truth:

“In the beginning was the Word, and the Word was with God, and the Word was God…and the Word became flesh, and dwelt among us, and we saw His glory, glory as of the only begotten from the Father, full of grace and truth…For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life” (John 1:1, 14; 3:16….NASB).

I’m not implying that Matthew, Mark and Luke never spoke of Christ being God or becoming a Man to procure salvation for guilty sinners, but their main focus was on Christ being sent to the nation of Israel as their Messiah. This is their central theme, though each writer also had another “theme” connected to this. It was given to Matthew to write of Jesus as the TRUE KING OF ISRAEL, thus his gospel begins with these words, “The record of the genealogy of Jesus the Messiah, the son of David.” The following verses (verses 2-17) prove that Jesus was born in the “Royal Line” and that He has a right to the “Throne of David.” Mark was inspired to write of Jesus as the PERFECT SERVANT so his gospel contains no record of His lineage or birth but begins (in Chapter One) with His baptism and entrance into public SERVICE. Luke begins his inspired Gospel with a very detailed account of 1) Jesus’ birth (Luke 1:1-2:20) and 2) Jesus’ genealogy (2:23-38) proving that He was indeed a TRUE MAN. He is constantly referred to as the “Son of Man” throughout his Gospel.

So, even though Matthew, Luke and John wrote of Jesus from a “different vantage point” (as KING, as SERVANT, and as MAN), their accounts of His life, miracles, the parables He taught, and His final rejection by the nation of Israel are all written from “the same vantage point.” In this way we can truly say they wrote as if they had all “seen together” (remember, this is what the word “synoptic” means) the events of which they wrote. I should add that there are still some differences (which are subtle at times) even when writing of the same events, but as we study those differences we see that they are often connected to the different focus they had on Jesus as King, Servant, or the Son of Man.  (380.1)  (DO)