1.) RF has these things called SkyDomes. It's basically a 'bubble' that is around your level mimicing sky. If you enable the sun and the moon, they will travel across the sky just like they do in real life. Clouds are also possible. Check the manual for more info.
2.) Yes. I'm not sure if it's possible with the built-in main character, though. You could
script the main character which would let you have more control over its actions and features. Writing the script(s) isn't easy though and I don't recommend it unless you are very familiar with the RF scripting language.
3.) I'm not exactly sure about this one. With the physics release by federico and some scripting... I don't see why it wouldn't be possible. But I believe it would be really hard, to say the least.
I'm sorry I can't give any more detailed answers. These things aren't exactly the easiest ones.
Welcome to the forums, I hope you have a good time with RF.

Pain is only psychological.