Q5.0.6: How do I start up a second shell buffer?

In the *shell* buffer:

M-x rename-buffer RET *shell-1* RET
M-x shell RET

This will then start a second shell. The key is that no buffer named ‘*shell*’ can exist. It might be preferable to use M-x rename-uniquely to rename the *shell* buffer instead of M-x rename-buffer.

Alternately, you can set the variable shell-multiple-shells. If the value of this variable is non-nil, each time shell mode is invoked, a new shell is made