?
There are multiple solutions, see the list at wiki.unipi.technology
Basically it depends if you want to use a free opensource solution (pidome,pimatic,…) or a completely different approach with proffesional solutions (Mervis)
Both solutions are possible. But remember there are only 12digital inputs (14 if you make a custom cable). But eg with mervis you can hook multiple unipis together.
Blinds are the same as lights, so yes.
Depends on what AC you have, most of them has infrared remo tecontrol which should be used....