This poem has 16 lines broken up into 4 quatrains (or 4-line stanzas).
Each line is comprised of eight syllables.
The first line is the refrain. In the second stanza, the refrain appears in the second line; in the third stanza, the third line; in the fourth stanza, the fourth (and final) line.
There are no rules for rhyming or iambics.
Kudos to Writer’s Digest for this summary.