if a skrox lose some skinks and a kroxigor, can i choose if heal the skinks or the kroxigor with regrowth? and if i heal a kroxigor only by 2 wounds, it come back with 2 wounds or i need to heal all the 3 wounds to take him back?
Regrowth has strict rules in the text of the spell. First you need to bring back any dead command models, then any wounded multi-wound rank-and-file (Krox in this case) need to be healed before you bring back any dead models. At that point though, you could choose to bring back skinks or krox. And yes, you can bring back a krox with 1 or 2 wounds, but if you bring one back, you have to heal it up fully before bringing any other models back.