WRT reploids not feeling cold, Zero in X8 complained about the heat in the Inferno level. If a reploid can feel hot, they probably can feel cold. I hc that the armor provides great insulation, but Inferno was in the middle of a volcano. It's probably chilly for them in the polar levels, too.
Oh yeah no I definitely think that they can’t handle extreme temperatures! You put anything in an extreme cold / extremely hot environment they’re going to have a hard time functioning. I think breathing (or external vents like Zero’s) helps them regulate their internal temperature to some degree, but of course that would only work to a certain degree.
I guess I should’ve clarified that I definitely think Reploids can feel hot / cold, but it wouldn’t bother them as much as it would a human (unless they’re in a volcano or the arctic, because then they have to worry about cooling / heating their bodies enough to continue operating). I know Capcom is pretty crappy at consistent storytelling sometimes, but small details like that do give some insight into Reploid biology. It’s fun to think about!