No the narrator of a poem is one who narrates, but the poet is one who wrote the poem
Polonius is using his daughter to spy her conversation with Hamlet. He teaches how to act naturally, how to walk and pretend that she is reading.
In that last phrase, he is saying that we humans often act in deceitful ways, for which we are to blame.
He admits that he is making a mistake, in teaching that kind of behaviour to his own daughter.
No because they generally get boring when it is the same actor or actress, I would rather watch many people perform together. Just my opinion
