1. Welcome to the forums!
2. This has been discussed before, try using the search function next time.
3. The general consensus is that the Nazi Party would not have become nearly as successful without Hitler. They would still gain importance, but the Weimar Republic would be replaced by an authoritarian-right government under someone such as Franz von Papen.
Japan would probably still end up in a war with the US, and lose. I think that Europe would not be very stable (remember Mussolini) but full-scale war would not break out.