Why are there green spheres on my Polaroid pictures on my instax mini 8 camera? Is it the film or is it my camera?

Those green circles are probably lens flares caused when a bright light source (e.g. Sun, indoor lamp) is nearly pointing towards the camera lens. The only thing to do is to avoid situations where there is that sort of bright light source pointing anywhere near the lens. The picture is "properly developed" after the quoted time for the Fuji Instax system - it does not change after that time.

On television news reports you often see similar rings of odd colours, sometimes a long line of them. So the problem is not confined to one brand or type of camera.

Usually green "spots" as you call them is due to lens flare. You can avoid this by ensuring the next time you take a photo with the Sun in front of the camera, that you place something (e.g. your hand, a piece of paper, etc...) in front of the camera so that it creates a shadow on the lens. This is why you see sports photographers with those big tubes, called lens hoods, sticking out from the front of the lenses. You can make your own with a cardboard tube from an empty roll of toilet paper or paper towels. Just cut the cardboard tube to a 1/2, 1, 1.5 and 2 inch length. Depending upon the angle of view of the lens, one of those lengths is going to be long enough to prevent lens flare, but short enough so it doesn't show up in the photo. You can make it look better by applying some primer and then painting it the same color as your Instax Mini 8. All your friends will think you're using some kind of secret accessory.

FYI - For clarity using the name Polaroid, instead of the term instant film or instant-film camera, to mean all instant-film cameras or photos is incorrect. It's like calling a can of Pepsi a Coke, or all cotton swabs Q-Tips.

Sometimes we get spheres when we use flash in a dusty environment

Green spheres are usually lens flare. Try pointing the camera away from the sun or bright light.

Internal refections or dirty lens.

It's a cheap camera