Perhaps it will be clearer if I put it this way: Since most religions require faith as a principal component of salvation - what do those who are incapable of it, do? Parasitic twins, the unborn foetus, etc.
It depends on how you define faith doesn’t it? There are of course numerous scriptural definitional texts, but it’s a lot like ‘love’. You can’t really know it by someone else’s description.
Whatever it is, again, it’s not a cognitive function, IMHO.
As for someone dead or brain dead, I dunno. It seems to me that whatever rule/law/effect applies has already applied.