I read about an experiment, in which they brought up cats in a room with no vertical lines. After they were released, they kept bumping into table legs. Similarly, if you lived in 4D but your environment was almost entirely 3D, you might learn to ignore the extra dimension in your retina, and it would just dissapear from your consciousness. You could do an experiment to test this in 3D. Put some mice in a thin glass thing like a big ant farm. When you release them, see how the extra dimension affects them.
Analogously I suppose, could the reason we can't see infrared or ultraviolet radiation be because they are too hot with daark-light for us to want to deal with?
That's probably part of the reason. Some animals probably can see other
wavelengths. Most are colour blind. Apparently birds can "see" magnetic fields, as if they have a compass in their head. If you hold a magnet near them, they don't know which way to migrate.
A dragonfly has wrap-around compound eyes with thousands of facets that can see in every direction around itself. Would this be considered a 3d retina?
No, it's just lots of 2D retinas. I'm not sure why insects have those eyes, it's probably something to do with being small. But it wouldn't need a 3D retina because it's only looking at a 3D space.
If you could see every part of the spectrum, detect all force fields, even see particles other than photons, like neutrinos, I wonder what life would be like. You'd be able to see the inside of everything, as well as the outside, just like a 4D being. Although initially the view would be different, your brain might adapt so that you feel like a 4D being watching the 3D space below. That would be similar to having a 3D retina.