New to Blender and 3d modeling in General

i have some questions.

  1. Does blender have an undo button?

  2. if I try to extrude, and tell it to only do the vertices, how can i go back and change it to do the edges. After I choose one or the other, it’s stuck doing it that way until i start a new project.

  3. How do I make a symettrical clone, where what you do to one object happeens exactly to the ohter, like in the video below?

to “undo”, do the classic Ctrl-Z, Alt-U show you a “Global Undo History” window.
To do “symmetric modeling” use the “Mirror” modifier.