Why did shakespeare's noble characters speak in iambic pentameter while commoners spoke mainly in blank verse or pose

Which pair of uses of figurative language from "the caged bird" support the extended metaphor of freedom versus oppression? back of the wind; floats downstream his wings are clipped; his feet are tied the caged bird sings; the free bird thinks dawn bright lawn; grave of dreams

What does the mother language reveal

What is the main source of irony in this poem? -the idea that winning is really losing -the idea that failures hold success in higher esteem than those who are successful -the idea that dying is winning