Can Emacs differentiate between ctrl-r and ctrl-shift-r?

Question

I\'d like to bind Ctrl + R to \'isearch-backward and bind Ctrl + Shift + R to \'tags-apropos

Answer 1

Yes -- one is "\C-r", the other is "\C-R". They can easily be bound to separate commands. For example, this should do the trick if placed in your .emacs file:

(global-set-key "\C-R" 'tags-apropos)