how it is possible to hit that mountain, and be in legal flight conditions is difficult to perceive
That's because I doubt you have ever flown in this condition. Your understanding (or I should say a lack of understanding) is very very evident.
Regardless of your Pprune status, it is likely you are a young pilot experienced in flying Caravans or hot air balloons whose only experience with whiteout is what you have read on the internet? Surely you are not an experienced, competent, reasonable and experienced widebody Captain?