Bash's broken history is what finally got me to switch to Zsh. The history behavior you want is: 1. each line of history is appended incrementally, but 2. each shell session only has access to its own history unless you specifically reload the history into your session. Every combination of history commands in bash didn't do the right thing[1], but Zsh's works as desired. [1] eg. putting 'history -a' in PROMPT_COMMAN…
No, only the last command. Very handy because that way you can start a new terminal and have your current history available immediately. I also have an alias r='history -n'. With this you can load the history of another terminal session directly into the current session.