How to select only a border of selected area? I selected some area and I need to get selected only border of this area. Does anyone know any function to achieve that? Or a script?
Select Boundary Loop

You can find the function in the Select Menu. 

It will select only the boundaries edges of the provided face selection.

As said in the manual's page:


  ...based on all regions currently selected, it selects only the edges at the border(contour) of these islands. 


Here's an example of usage: