Are there any playable offical unreleased prototype vb-roms which work on flashboy?

Yes.

Which ones are out there? I know about Bound High, but I was wondering what others there are…

Bound High
– Review here

Space Pinball
– Review here

Faceball
– Info about the proto on Project:VB
– Retrogames reviewed this (unfinished) proto.

V. Bowling
– Info about a proto on Project:VB

Insmouse US version
– In the hands of ASSEMbler

Dragon Hopper
– Must be somewhere 😉

thanks KR155E, i see, this topic has been already discussed many times in the forum.