Mutations as skill upgrade and Corrupted

Hi Folks!
I have a few doubts about mutations related with cult of the possessed and mutations adquired with a Skill advance in corrupted.

-First of all, Cult of the possessed Mutants and Possessed can buy mutations when hiring but the second one cost double.



-Then we have Mutant skill from Chaos Marauders, that says you can take one mutation from the Cult of the possessed.



-And finally we have Corrupted Characters where says you can take mutations or blessing instead of ans skill if you are a follower of Chaos.



At this point i have these doubts:

-Aquired mutations by skill advance cost always the same? we are not talking about hiring mutations fee from cult of the possessed where exactly says WHEN HIRING.
-Blessing counts as mutations?
-All mentions of Random Mutations Charts from cult of the possessed like Burning Town Border Random encounters are replaced by Corrupter Characters ones?