A.1.1 How to show git’s output?

To show the output of recently run git commands, press $ (or, if that isn’t available, M-x magit-process-buffer). This will show a buffer containing a section per git invocation; as always press TAB to expand or collapse them.

By default git’s output is only inserted into the process buffer if it is run for side-effects. When the output is consumed in some way then also inserting it into the process buffer would be to expensive. For debugging purposes it’s possible to do so anyway by setting magit-git-debug to t.