1)It supports mesh deformation, if that's what you mean.
2)I think there might be a cut off with limbs or objects somewhere in the millions so for the most part, yeah your graphics card is your limiter.
3)No, I wouldn't go as far to say it's a whole other language (consisdering the both origin from BASIC), but many of DBP features have been reworked, because of these upgrades DBP is not Compatable to DB Classic or DB Enhanced.
Teenage Male Geek + Female Remotly Interested in Common Geek Activities = Teenage Male Jackass