I can really only answer one of your questions from personal experience.
I weaned my then 21 month old DD so that I could use clomid to fall pregnant (noting I just went with the fertility specialists advice to not take clomid and breastfeed, however as MadB recommended, in hindsight, I would definitely look into it further). My DD however was only on one feed a day at that stage.
While i was pregnant DD asked maybe ten times if she could have some booby, to which i replied there was no milk but she could have some when they got milk in them. In the six weeks since DS has been born, DD asks maybe every second day if she can have booby (usually while DS is on them), and I tell her she can have some after her brother. She usually forgets and if I remind her she brushes me off. A couple of times I managed to convince her to get on my lap and she has put her mouth on my breast but not in a way to get milk. When I try to attach her properly, she won't have a bar of it and she strangely almost seems embarrassed by it. I was really hoping she would start again, but I haven't pushed it........ seems she has been okay with the weaning, but i haven't!!!