Maybe it does not need to be instinctive because women have seen other wome do it for eons, at least until the 20th century came along.
Probably not, but in a blue lagoon situation, you would probably have held the baby in your arms at some point, and he would have shown you what breasts are for.
I would guess that this is a big part of the answer. Adult humans actually don’t do very much by instinct - we’re trained by our cultures. That’s the way we’ve evolved in general to work (compared to less complex animals like, say, bees or ants, which seem to be almost entirely ‘hard-wired’)
So as far as caring for a newborn goes - yeah, you figure out how to do it not by instinct, but by tapping into the accumulated knowledge of your culture, like you figure out how to get food, or keep yourself clean.
As far as the giving birth process is concerned, my experience is pretty similar to carlotta’s - let it all just happen, and it will pretty much all just happen (Absent anything going horribly wrong, of course, but in those sort of cases you probably can’t do much about it anyway - you need help from somebody else there at the birth)
Not necessarily. Instincts in humans can be pretty vague, and work like built in guidelines that make it easier and more likely that we’ll learn whatever the instincts in question are evolved to promote, instead of the kind of rigid pre-programmed behavior you’d see less intelligent animals. To use Zsofia’s example, if your baby is crying your probably at least in part instinctive reaction is likely to be to pick it up and hold it close to comfort it; and from there you’re already pretty close to nursing it. And given that human mothers probably are going to see other women nursing, the instincts involved don’t really need to be very detailed.