Just finished Kyoukai no Kanata anime and both movies

[Nanadaime_Hokage]

I just finished series and movie and I searched but couldn't get the exact answers I was looking for

so please just tell me some things

How did Mirai come back after dying?

In the starting of second movie Mirai clearly had her memories at first but after meeting Akihito she lost it, why?

Who is Kanbara Yayoi, how she knows everything and what is the actual relationship of her with Akihito? (we got a hint saying she is the gatekeeper and is ancient)

And who are these three people at the end of Mirai-hen? (From the looks of it left one is Izumi but who are other two?)