"in the past." The implied information is that this refers to the time when the people started rebuilding the temple. (See: [[rc://en/ta/man/translate/figs-explicit]])
The implied information is that this is the remnant of the people who returned from exile. Alternate translation: "the people who returned from exile" (See: [[rc://en/ta/man/translate/figs-explicit]])
Yahweh speaks of himself by name to express the certainty of what he is declaring. See how you translated this in [Zechariah 1:3](../01/03.md). Alternate translation: "this is what Yahweh of hosts has declared" or "this is what I, Yahweh of hosts, have declared" (See: [[rc://en/ta/man/translate/figs-123person]])