Answer 1

No, learning Django is not mandatory to learn for Python 3... even if you want to use Python at back side of a web project: Django is probably the most powerful web server framework for Python, but not the only one at all... I myself have a preference for minimalistic frameworks when I resign myself to use one, so about web server, I have a few explored Bottle rather than Django (Flask seems to be a good intermediate also, between the excessive minimalism of Bottle and the squandering of Django)