No, the past has been altered entirely and no longer exists, therefore what HAD been the past, is now no longer the past
Yes, although it has been changed and has not happened in our perception of time, at one point it was happening before it had been changed
Thinking very simply here, whatever happened before you went back and changed the past would only exist as a memory.
The only way time travel into the past is possible is with the parallel universe theory. So assuming you traveled into the past to help the Axis win World War 2, you would be living in a parallel universe. There would be the universe you came from where the allies won world war 2. However, you would be in the universe where the axis won world war 2.
Leaving the parallel universe theory out, you couldn't back in time and changed it because a time paradox would occur. Lets say you went back in time to kill Winston Churchill. Well you couldn't kill him because if he was dead you wouldn't have gone into the past to kill him.