The maximum number of VDs you can configure with snapshots varies by model from 16 (V100 series), 32 (Q500 series) to 64 (P400/600, F600/630). 

Yes you may create a snapshot schedule for a dedicated virtual disk, and even automapping the snapshots taken by the schedule with LUNs.

Before taking a snapshot you'll need to assign a snapshot space for the virtual disk to keep the snapshots. After the snapshot space is assigned, you may simply choose the "take snapshot" option from the virtual disk options, or alternatively in the snapshot management page, select "take a snapshot" for any snapshot ready virtual disk. 

A snapshot is more like a image taken at a dedicated point of time, recording the complete status of data inside a virtual disk. 

If the two systems are the same model and using the same firmware version, then roaming the RG between the two systems is possible. If however the two systems are different models or using different firmware versions, consult Qsan support team for the possibility.