How to find\extract unique symbols in a piece of text?

What program do you use to look at these things? There is a menu at the top of the screen. I suggest you click on every item in that menu and see what options you have. The same is true in every program you use. If you are using Windows you can click on the "START" icon at bottom left and get a menu of menus. You should inspect every detail of every item in that list. You don't have to memorize everything, just remember that they are there. For instance if you want to turn your monitor sideways, most video cards offer an option to rotate the picture. When you have done all this, then you can claim to know how to operate a computer at the beginner level.

For this particular question you are looking for "FIND". In most programs you can get that function with Ctrl-F. So highlight a character, press Ctrl-C, then Ctrl-F, then Ctrl-V and see what happens.