I would like to play multiple videos consecutively. In other words, after the first video finishes, the second video begins automatically, and so on, without requiring the user to select the next video in the series. Is that possible?

When I do this:

m4v}1_intro{/m4v}{m4v}2_topic_A{/m4v}{m4v}3_topic_B{/m4v}

I get multiple play windows for the user to select; but can I combine them into an "automated playlist"?

Hi. No this cannot be done. Playlists are not supported.

The info on www.joomlaworks.net/extensions/free/allvideos says that playlist are supported now.
How can I add a playlist?

This refers to Youtube playlists not custom playlists. If you have a playlist on Youtube just enter the URL and it will work.