Hamira Saknata from Isura in the question of a rabbi

Assuming that “and you have made a rule that is long, you shall not depart from it” is still valid today (probably not), and assuming that there is only one lucky person who meets the definition (Rabbi Kanievsky),

1. Do I have an obligation to listen to him even when in my opinion it borders on protecting one’s life, or can it be said that there is a greater danger than a prohibition even in relation to the prohibition of “not to deviate”?
2. In general, when the rabbi’s decision is on a question of reality, for example, according to the rabbi, there is no epidemic here that borders on endangering lives, or at least not one that arouses reasonable concern (I have no idea if this is his opinion, but let’s assume it is), can it be said about this that “you shall not deviate” is essentially a matter of conduct and not a decision of truth, or that when the decision-making body seeks to decide on a question of reality, I have no obligation to obey it.

2.