Version 1.0 is no prototype. It's just a bit more rare than 2.0 and 2.1. It shows up now and then on auctions and stuff. I read on a Japanese message board that one guy bought Family BASIC back in the day and got 1.0 and then his friend bought it only months later and he got 2.0. He then called Nintendo and they let him trade it in for a 2.0 cart.
Check out this thread
about version 1.0, a guy that dumped it too.
All versions of the cart required two AA batteries and had a back-up enabling on/off switch.
"Required" is a misleading word I think. AA batteries are only needed if you want to use the backup feature which can only be used for certain things (in V3 it can be used for more things though). You can still save to tapes without it.
Known versions of NS-HuBASIC:
Earliest known version. The PlayBox BASIC prototype
ROM seems to have this version.
V 1.0PlayBox BASIC (release version)
and early Family BASIC carts has this version.
Pressing T at boot activates a RAM self-test screen (confirmed in Family BASIC but not in PlayBox BASIC).
The RAM self-test screen is turned into a short-cut to BASIC mode. The command SCR$ was added.
Some buggs are said to be fixed. I don't know what kind of buggs though.
Used in the red V3 cart. Tons of new commands and features are added. The non-BASIC stuff is gone, more Work RAM and there are sample games in ROM.