As Mikequeen123 says, there are the 12 principles of animation, which is a good starting point. Learning animation can be a very deep subject, and it’s best to start at the beginning. Start by doing simple animation exercises, like bouncing balls. Exercises help to develop an ‘eye’ for what you are doing.
No, not really. A bone needs a starting pose, and then it needs to hold that pose, until you want it to move. That’s why you need both of those keyframe, otherwise, how would blender know how long you want to hold the pose for?
Good animation actually takes a lot of work… the computer just doesn’t do it automatically for you…