Yahweh uses this question to emphasize that he is the one who has done these things. Alternate translation: "I have performed and accomplished these deeds." (See: [[rc://en/ta/man/jit/figs-rquestion]])
Here the word "generations" represents all of human history, which Yahweh created and directed throughout history. The rhetorical question anticipates the answer, Yahweh. Alternate translation: "I have summoned the generations of humanity from the beginning." (See: [[rc://en/ta/man/jit/figs-rquestion]])
These two words mean basically the same thing and emphasize that Yahweh is the one who has done these things. (See: [[rc://en/ta/man/jit/figs-doublet]])
Possible meanings are 1) that Yahweh existed before creation and will exist at the end of creation or 2) that Yahweh was before the first generation of humanity and will be at the last generation of humanity.