The standard select and back buttons can be changed in the input setting. As for left analogue stick load a nes game, open the quick menu, scroll to controls and change "user 1analog to digital type" to left analog, then scroll down to "save core remap file"
Edit, it appears you are trying to setup your nes controls in the main user interface, this is why confirm and back are changing. Setup your nes controls in the quick menu with a rom loaded like I said above.