what size background images I need for ios devices

I am just trying to learn iOS development using xcode. I want to create a background image that works on all iOS devices. Of course the background image suppose to take the whole screen. Do I need to create a multiple images for different iOS devices? If I am using photoshop to create these images, what should the size of my images?

for example in apple guide, I see For iPhone 6: 750 x 1334 (@2x) for portrait 1334 x 750 (@2x) for landscape

For iPhone 6 Plus: 1242 x 2208 (@3x) for portrait 2208 x 1242 (@3x) for landscape

does this means I have to create the same image in 4 different sizes to work for iphone 6 and and iphone6 plus? what other sizes I need for iphone4, 4s, 5 and 5s?

Thanks