The nic I have no idea about but I don't think it would be that hard to extract nicotine into an ethyl alcohol. Of course if there are any experts on this please let me know if I'm wrong.
As far as CC goes: it doesn't taste a lick like a cuban cigar. I've had quite a few and are quite sure of this. I actually found the CC flavour to be quite revolting IMO. However, none of the tobacco flavours taste like tobacco to me. (Um, I sell cigars for a day job JIC you were wondering.... I'm a bit of a snob when it comes to tobacco for a point of reference.)
As far as the juice goes, I've let cartos uncapped for over 2 weeks before with no juice loss that I could notice. It was a blueberry carto that I thought was empty till I did a reverse Taryn Spin and got a full cartos worth of juice out of it. I vaped it after putting the juice back in; just as yummy as ever.
My friend left a carto untouched and uncapped for over a month with, again, no discernable juice loss.