Question

In Emacs we can scroll inactive window using certain commands

But not all details are listed in the manual.

C-M-v can scroll down the other window

my intention is to scroll up the other window, how could I do that ?

Answer 1

Try C-M-S-v, which is scroll-other-window-down.

You can find such key bindings by doing C-h b (describe-bindings) which populates the *Help* buffer with a list of all the key bindings and associated commands for the current buffer. A quick search through that for scroll-other showed the binding you mentioned, as well as the one I listed.