Echoing the introduction in your conclusion helps readers come full circle. It helps them see how you have developed your idea from the beginning to the end.
By issuing a challenge to your readers, you create a sense of urgency, provoking them to act to change the status quo.
Looking to the future is particularly relevant when you are asking readers to take action. To move readers to action, you must establish the persistence of a problem and the consequences of letting a situation continue unchanged.
Posing questions stimulates readers to think about the implications of your argument and to apply what you argue to other situations.
A quotation can add authority to your argument, indicating that others in positions of power and prestige support your stance. A quotation also can add poignancy to your argument.