Is it possible to turn off the new "auto save to whitelist" advanced feature so it is a pure whitelist blocker?

No way to turn off the "auto save to whitelist". Unfortunately sometimes unwanted callers do press "0". I had mine setup for 2 or 3 days when one of the computer support scammers dialed 0.

If a new caller presses zero will he be able to leave a message on my answering machine?

Yes,surely,it can work.For since the new caller presses zero,their calls were added to white list forever.And at this time,if you don't pick up the message.Then caller can leave a message to your answering machine as normal.

Any products with - contacts go through, non contacts go to answering machine, blocked #'s get hung up on?

I would also like such a new product. It could just trick the phone answering machine to answer with 10 fast rings or such. That would also say don't answer to me. I hope they create it soon, I have #1 and buying #2 and will buy your version when they make it.

Versions 1 and 2 look alike. How does one tell the difference between these 2 units? Is there a model number or version # printed on the units?

The photo on Amazon for the Version 2 is actually showing a Version 1 which adds to the confusion. There are three identifiable differences between the models. 1) Version 2 does not have the Sentry symbol before the Sentry label on the device. 2) Instead of the language labels under the VOICE button, version 2 has A/B/C/OFF. 3) When turning over the device, version 2 has a battery compartment while version 1 does not.