1.- Can I use this NAS Unit with Hyper-V, someone in the community has been able to configure
2.- Two units can be configured in mirror
3.- Can I connect more units for additional storage (stack)
Would you like to use the NAS as host for Hyper-V or just as storage?
If we are talking about storage then this would be possible but very slow because you need to use it via a network share.
Two units in mirror? So you want a sync between them?
What do you want to achive with stacking? Adding more space to the share?