Yeah I would say new Israel, but also a continuation. The old being less inclusive and the new being more inclusive with the rapid expansion of gentiles.

No, there's nothing magical, but it was symbolic of the New Israel. Since there were 12 tribes of Israel, there were 12 apostles to show both continuation and a renewal of God's people. Jacob had 12 sons, so there were 12 tribes.

> What separated that group from "the twelve"

Mark 3.13-14 says that Jesus specifically called 12 that were "those he wanted, that they might be with him and that he might send them out to preach." That's what separated them out from any who chose to follow Him.

> Yes of course we all know about the 12 tribes of Israel but we also know that the 12 did not in fact represent all the tribes.

Numerologically speaking, "12" in the ancient world came to symbolize completeness.

Is there some magical value for having 12 apostles as opposed to 13 or 100?

What is clear through scripture is there was a much larger group of "hangers on" surrounding Jesus during his ministry. What separated that group from "the twelve" and the selection of Matthias from amongst them after Judas died?

Yes of course we all know about the 12 tribes of Israel but we also know that the 12 did not in fact represent all the tribes.