Please help me out with this Photoshop noobie list of questions

I will list different things that I have no clue how to due and hopefully u guys might be able to help me out…

  1. How do you curve lines?
  2. How do you curve the corners of squares?
  3. HOw to you make the edges of a circles (or any shape) look to be fading away. (no rigid border, just a transition).
  4. How do you make a line fade out or add a gradient effect to it?

Thank you very much if you are able to answer even one of these very simple questions.