1. Yes, quad-buffered stereo is only available on Quadros. However, you do need to render both eye viewpoints in your application using the GL_LEFT and GL_RIGHT draw buffers.
2. If you want two display walls displaying the same thing with passive stereo, you'll need to use two GPUs and either configure Xinerama clone mode or use SLI Mosaic.
3. There are some technical differences that make NVIDIA 3D Vision better suited to LCD monitors, while the old-school glasses (at least the ones I've seen) are better suited to CRTs. In addition, 3D Vision Pro lets you use RF for synchronization instead of IR, which works better when there's a lot of interference in the IR spectrum (multiple emitters, fluorescent lights, daylight, etc.) Due to difficulties in Linux's USB subsystem, you currently still have to have the 3-pin DIN cable connected to the stereo emitter.
4. You should be able to have two active stereo displays on a single GPU.
5. Genlock and framelock refer to a board that connects a pair of GPUs together and synchronizes their displays. You can also network these boards together to synchronize multiple PCs. You need this for active stereo across multiple GPUs because otherwise their displays are driven by different clocks that might drift. See here for more details:
6. Yes, you should be able to.