There is also a long law in the near body, also called exclusion law. No matter whether it is a metrical poem, a metrical poem or a long rhyme poem, we must strictly abide by the metrical rules, including leveling, rhyming (long rhyme can be changed, but it should also be flattened), fitting and so on.
Classical poetry is not so limited, as long as it rhymes (both rhymes can be used or rhymed).