Intention and authority

Hello Rabbi, a few questions:
 
1) A person who keeps a commandment because it is written in the Torah, who is strict about both easy and hard things, but does not believe that they originate from God, is he considered to be keeping a commandment? (Is his taste folkloristic or something else strange)
2) A person who fulfills the commandments of the rabbis because they must be listened to according to the Torah, intends to fulfill the commandment "and do as they instruct," but in his mind disregards the mitzvah and the meaning of the mitzvah (the rabbi). Is he considered to have fulfilled the mitzvah?
3) I assume you wrote about this in the past, but I don't know where: Why is the Rabbinate not considered to be "and did as you were told" today? Maybe you'll say that the ordination was simply lost and therefore there is no Sanhedrin, and then I answered myself. Is there any other reason? Why don't we listen to them from the "Dina Demalchuta Dina" law and it simply seems that since the state recognizes them as the religious entity, we should listen to them as a religious entity? (Maybe the state itself doesn't listen to them in some things, and then of course I didn't say anything)
 
4) Does "making a rabbi" according to Tractate Avot obligate me to follow the rabbi I "made" for myself?
5) In the future, would you prefer to ask each question in a separate post?