It was billed as the Baby Partner.
No. The original Partner 206 module that could be used standalone or as an expansion module for Partner ACS, Partner Plus and Partner II was the "Baby Partner".
The Endeavor was a stripped down ACS with features missing. Sold for a few dollars cheaper. IMO not worth the trouble.
The processor looked like an ACS but had only one card slot. It could be expanded with as many as four 362EC expansion modules. You could use it with a 2- slot carrier out of the box but if you wanted to use it with the 5-slot, there was an expansion PC card that you had to put in the card slot. (I have never had to do that, and I believe I used the 5-slot. The Endeavor was modified several times in its thankfully short lifespan where they made it and the 362's more compatible with the ACS. So, I assume needing to do that was eliminated for anything later than the first release.)
There were Endeavor phones (as expected, stripped down Partner phones with something missing... the bases. Nobody ever used them and instead just used regular Partner phones.)
To answer your question, you can use either VM card with the Endeavor. I assume once the processor is upgraded to work with a 5 slot you can remove the upgrade card freeing up the card slot, if you need to do that and can get an upgrade card.
I know I sold ONE of those things. Installed it in a drugstore. Maybe a couple of more.
-Hal