learning the interfaces and working with a a cylinder

Hi, Still playing around with the interface and watching tutorials and watching the Blender Cookie tut. on modeling…they are showing modeling with a cylinder. While I watch tuts I try to follow using Blender 2.72b…just did the download a day or so after I saw it up. I also am writing things in a notebook so I can learn the names of ares and controls and what not. So when I add a cylinder…I was playing with adding a cylinder…I added it and was playing with vertices, looking at how round I can get it or less round by entering the number to see how it varies . I got it to a Hex shape…6 sides… then went from object mode to edit mode and playing with selecting sides… Feeling like I am starting to get a better understanding ,I want to change from 6 sides to a smoother cylinder…not to make anything but, just so I can learn controls and stuff. If I try to go back to “object mode” because thats where I had already started with cylinder …the area on the bottom of the tools(left screen toward the bottom) where the add cylinder and adjusting vertices,radius, depth was …that disappears and its basically history and toggle edit mode. I figured if I went back to where I had started maybe I can just redo the vertices there…or radius … So if I start to edit and want to change the number of sides…How do I do that where I can basically go back to that area where I can edit those settings. I thought maybe something should be obvious but as barely a newbe its still a foriegn language lol…Also if you split and add screens for different views and such is there a way to go back to your default view with a single short cut, without having to join the screens?

If I try to go back to “object mode” because thats where I had already started with cylinder …the area on the bottom of the tools(left screen toward the bottom) where the add cylinder and adjusting vertices,radius, depth was …that disappears and its basically history and toggle edit mode.
Those options are ONLY available when you initially add the object

So if I start to edit and want to change the number of sides…How do I do that where I can basically go back to that area where I can edit those settings.
Delete the cylinder and add a new one with the correct number of sides

Also if you split and add screens for different views and such is there a way to go back to your default view with a single short cut, without having to join the screens?
At the top of the blender interface there is a dropdown list of screen layouts. Duplicate the default layout before you do anything so you always can just reload that to get back to the default