A few as yet unanswered questions about the plugin API

I've been developing MuseScore plugins for almost a year now, but there are still a couple of unanswered questions I have. I would gratefully accept your insight into these questions:

1) When EXACTLY should one use curScore.startCmd() and curScore.endCmd() in your plugin code? I find sometimes I think I need it (e.g. when calling cmd()) that in the logs it says that endCmd() had 'no command active' — I'm guessing that means I didn't need to call startCmd()/endCmd(). However, sometimes if I don't use it, MuseScore doesn't see things changing and gives me the wrong values for things. I've also found that I can crash MuseScore if I don't adequately wrap things in startCmd()/endCmd() and then the user hits 'Undo', or you quit MuseScore and it ungracefully crashes.

2) I'm using cursor.add(elem) inside a loop to add a bunch of elements. Can I call startCmd() once before the loop and endCmd() once after the loop, or do I need to wrap each individual call to cursor.add() in startCmd()/endCmd()??

3) What exactly does cursor.inputStateMode = Cursor.INPUT_STATE_SYNC_WITH_SCORE do? I don't entirely understand whether I need to use this or not.

Thanks/Merci/Grazie in advance