You have asked more than one question so I have had to edit it down according to enotes regulations. This excellent story by Rad Bradbury presents us with a society that has attained a ridiculous level of technological sophistication - the house is shown to do everything necessary, making the need for humans absolutely redundant - which is ironic in itself because there are no humans now and the house continues on without them. However, one of the key themes of this story is the ephemeral nature of human civilisation and achievements - in spite of the incredible advances made by humanity in this story, nature is shown to be superior and triumphs over technology, symbolised by the destruction of the house.
A key way this theme is presented is through the poem recited by the "voice," which says:
And not one will know of the war, not one
Will care at last when it is done.
Not one would mind, neither bird nor tree,
If mankind perished utterly;
And Spring herself, when she work at dawn
Would scarcely know that we were gone.
This story ironically presents us with the truth of this reality, as we are shown nature indifferent to the existence of humans or their extinction, carrying on as normal. Our great technological achievements and our advancements are nothing in the face of Nature, who "scarcely notices" the absence of humans in this story.