1) There is no way they can promise the return they are saying
2) They will MOST probably convert your BTC somehow
3) Golden visa or not (for not EU citizen), you have to live minimum 5 years in Portugal as main residency (and more than 183days a year) AND you have to pass official portuguese language test to qualify too.
The technical side of getting a passport was not as interesting to me in this whole story as the question of how deep the adoption of bitcoin for the governments' own settlements can go. But here, unfortunately, judging by where the discussion is going, it turns out again that someone decided to use a popular topic for his own promotion, and there is nothing fundamentally new. It's a pity! I will still wait until large countries finally mature enough to officially include bitcoin in their foreign exchange reserves.