I think so, yes.
i don't think that 10 year gap is accurate but girls do mature earlier, reach puberty earlier. it has even been shown that female newborns are born a little more developed than male newborns (even when both babies are born after same number of weeks into pregnancy). not sure why this occurs though..
no. that is myth ba<x>sed on girls hitting puberty earlier in life than boys and by a flawed hormone research study.
Not that much. Girls are just designed by nature to mature earlier than boys, but it's only by a couple of years or so.
10 year? No. But if you talk to a 14 year old girl and a 14 year old boy they (typically) seem to be worlds apart. I think there are a lot of well-documented biological and social reasons. But a 22 year old woman and 22 year old man are less likely to have a huge maturity gap.