“You can double-click on a style in the Paragraph Styles or Character Styles palettes to edit that style. However, if you have text selected, you'll automatically apply that style to the text! If you want to edit the style but not apply it to the current selection, hold down Command-Option-Shift/Ctrl-Alt-Shift when double-clicking on the style.”
“While I select a text frame; I hold down Ctrl-Alt-Shift (Windows) keyboard shortcut and double-click on its style in the Paragraph Styles to edit the style without applying to the current selection text; but when I manipulate the style settings, the selective text changed in real time! Please correct me, I confused??!?!”
Sounds to me like you have the Paragraph or Character Style already applied. You have the TEXT FRAME highted – not the TEXT within the frame.
If a style is already applied to your text – then changing the Paragraph Style will alter the look of the text – it changes in Real Time when you have the PREVIEW icon ticked in the bottom corner.