Can't change startup disk iMac

Here is my situation: I've only the mouse paired with my iMac because I rent the keyboard to a friend. Unfortunately the startup disk is set to a fallacious Windows partition that don't want to boot. It sucks on "No bootable device -- insert boot disk and press any key" so I can't boot in any working partition. So, I've two questions:

• There is a way to change boot partition or to go to recovery using only mouse?


• If I buy a standard usb keyboard, can I just plug the usb cable and use it to change the boot partition or it won't boot, because of the drivers?