can i create a floating window function as Shelf?
I'm not clear on what you want to accomplish. If you want a shelf button that will pop up a floating window, then yes you can do that.
If you mean something else, you will have to explain what you are after in more depth.
the least thingi want to do is just a floating, resizable shelf window
and the better thing i want to achieve is to make a shelf area in one of my character selection custom UI
any idea?
Look at "myshelf.mel" from Bryan Ewert. This should show you what you need to do.