It has wifi and can update databases or firmware etc (which works very well) but you have to use your phone as a hotspot / have wifi in the hangar, etc.
1) yes
2) no, but I wouldn’t be surprised if it comes in a future update.
3) yes
You will need a GDL50 for the ADSB as far as I know.
More expensive than an iPad + software.
Less battery time.
Inferior software.