1. - means that the person is adaptable and able to alter course as the situation demands without having major difficulty.
2. - metaphor for an impossible task -- or something that can not be done.
3. the "skin" of your teeth is very thin, so your success was by a very thin margin, almost didn't succeed.
4. A dime is small, so when you turn on a dime, you turn quickly and
very sharply. In reference to decisions, very small events would
make you change your mind rapidily -- you would turning on a
dime. In reference to a vehicle, it would refer to having a very
tight turning radius.
Hope this helps