Do rafflesia protect themselves by producing poisonous sap,having brightly coloured petals,emitting foul smell,having sharp thorns orany other ways?

It doesn't seem too much for protection. It has a flesh rotting smell which would repel humans, and some animals, but attracts beetles and flies. The beetles and flies are good for it because they pollinate it, similarly like bees do to most flowers.

Even through its acrid smell, shrews and some other small animals are known to eat its fruit, and through defecation, spread its seeds. It is a parasitic plant, having root like structures in vines. It only exists in Asia.

Rafflesia - Wikipedia, the free encyclopedia