In the form of time travel being talked about, the answers are:
a) Yes, you disappear from the time you were in.
b) Yes, you're in two places at once for the duration between your arrival and your departure
c) Forwards travel in time doesn't cause too many philosophical problems (since we're already doing it) which is why nobody talks about it. But there's no requirement to wind up exactly where you started.
a) Yes, you disappear from the time you were in.
b) Yes, you're in two places at once for the duration between your arrival and your departure
c) Forwards travel in time doesn't cause too many philosophical problems (since we're already doing it) which is why nobody talks about it. But there's no requirement to wind up exactly where you started.