All mammals have only seven neck bones, What about non mammals?

No. The extinct marine reptiles of The Jurassic, like the Mosasaurus or the Plesiosaurus have more cervical vertebrae.

I don't know about most non mammals but insects don't even have a skeleton on the inside. They have an outside skeleton called a n exoskeleton. They don't really have bones as we would think. Its more like a hard shell. So I would have to answer your question with a no . Because the animal kingdom of insects does not.