Short answer: Nope.
For your first question, I know it can't be done, but I'm curious as to what you're trying to do that would require that.
For the second, the problem there is that is a lot of calculations to be doing all the time, especially compared to a pre-keyframed-and-exported animation. Since their target ...mmmm genres, lets say, are so different, it really doesn't make sense to compare HeroEngine and UDK. The ability to expose inverse kinematics to the engine so that it may adjust them (making feet line up properly with sloped ground) is a rather complex thing.
For the bow example, you could certainly achieve a similar affect with clever blending between different animations. It's difficult to understand and get working, due to the complexity of authoring the necessary animations, but you might look into Additive animation sequences.