How to answer part A of the OP? Should I answer as an umpire, or as a former assistant SID who also did the baseball public address announcing?
What the hell, I'll go with the latter:
If it is the visitors who are sending the wrong batter up, you announce the wrong batter's name loudly and drawn out (so your team's head coach starts thinking to himself: WTF?).
If it is your team who is sending up the wrong batter, you announce the proper batter's name so that the wrong batter will stop dead in his tracks.
😃😃😃😃😃
Seriously (as this is an umpire board) I have no changes to what was posted above.