Babies - question 1 is hard to answer, because sometimes, breastfeeding has not got off to a good start, and supply is already dwindling. Offering another side is a crucial part of addressing this - the more often breastmilk is removed, the more quickly it is made and this of course means overall, more milk. But in the short term, in very extreme cases, a temporary top up may be needed if a baby's dehydrated, or clearly under-nourished....I think top ups are suggested far too casually, and any formula given to a bf baby should be seen as an intervention, and the pros and cons carefully weighed up.
It would be better for the baby to have a top up of donated human milk, or expressed mother's milk - this can be useful if the baby is losing interest in the breastfeed, as the top up of EBM can re-ignite this interest.
I don't know the answer to no. 2. I expect the real answer is that it is normal for all humans to wake in the night, sometimes several times, but they can learn to get themselves back to sleep with varying degrees of speed and 'skill'. So in pre-industrial society, where it was/is normal for families to sleep together, babies and young children probably breastfeed on and off in the night to help themselves get back to sleep. When they gradually stop bf, a snuggle into whichever body is closest probably helps them get back to sleep!