Click the switch you use to select which side mirror you want to alter that is what turns the mirrors dropping when selecting reverse.
For the warning, have had 2 different actions depening on how old the car is, my RX you had to accept before displayed but then it was always on the satnav anyway so just pressed it when started the car, the ISF shows the message but auto times out after a few secs anyway (think the change was about 2010)