To learn the engine? Doesn’t matter imo. If you already know C++, you can get comfortable with Unreal C++ in no time. If you wanna start making games right away however, you can consider learning blueprints first.
No, but here’s the most basic one out there. After that, you can start a demo project where you set your own objectives, do some research when you encounter an obstacle, and implement it to fit your use case!
Hope these help! 