Can 'it' be used of a child?

Sure Tang though I don't like the sentence as written because of the implication that the two events are not intimtely related. I'd probly say,

The instant a child touches a hot stove it immediately learns not to do that again

Yes, but only if it is a hypothetical child of unspecified gender.

Thanks, centrox.

Suppose my friend and I see a baby. Can I say to my friend "Look at the baby. It's cute."

Yes, it would be the natural thing to say, but the child's parents might be offended if you used 'it' when speaking to them. One first enquires the baby's gender.

Thanks, centrox.