Post can be deleted in between 5 minutes of time frame of writing the post and after 5 minutes there will be no option of delete the post. As this system is made on blockchain technology you cannot even delete anything in this blockchain.
You also cannot delete your steemit account as it is blockchain technology everything is stored in a data and blocks.
So likely if you copy paste content you will be in eye of bots and you even cannot delete the post after the bots identify you.
be ware and stay safe