Answer:
The line 'So Eden sank to grief' is an allusion, or literary reference, to the Biblical story about The Garden of Eden, a perfect paradise until Eve ate from the Tree of Knowledge. By making this reference, Frost is implying that the idea nothing good can last is an old one; it's part of our human experience.
16.985 in word form is sixteen and nine hundred and eighty five thousandths.
In New Amsterdam slaves had some opportunity to make money and could buy half their freedom. I believe so
The theme is the central message in a literary work!
Hope that helped, even though it was slightly late :D
