I think my answer to your question in the subject line would be "at the time, or with hindsight?" :-)
Seriously, my reaction to people being astonished that babies can learn letters at this kind of age is mostly that this is absolutely trivial compared with what all babies are doing at this age without anyone thinking it's remarkable - learning language! Not to mention the enormous amounts of information they're picking up about everything else. When you come to think of it, that they can learn to connect 26 symbols with the sounds that are their names is really neither here nor there.
I'm not saying that your DS isn't gifted! He may well be, especially given that you are. However, I don't think there's any way to be sure now, or indeed, any need to try to be sure. In answer to your qs I'd say: (a) Maybe (b) Varies enormously, and depends on what you mean by "accurately identified". IQ tests are often said to be not all that reliable before the age of 6 or 7, in the sense that they can be administered much earlier, but if the number doesn't reflect a parent's experience of the child, the experts here will mostly suggest that the test may be wrong. If we ask instead at what age a parent can feel reasonably sure that their own child is gifted; well, many here (including I) have felt pretty sure about our 2yos, but then, how many parents of 2yos have felt sure their children were gifted and then changed their minds once the children were 5? We don't know, because those parents are not here to ask. Fortunately (c) No, not this early (d) Do exactly what you'd do with any child: have fun, follow your child's interests, help your child to learn about the world. All this is IMO and just my 2p-worth of course. Have fun!
