What are the mitzvos that are not forever?

Question

This Shabbos, someone noted that the Sefer Hachinuch says that there are no mitzvos at all in this parsha (Bamidbar). I responded at once, That's absurd. It seems like it contains dozens of mitzvos!
Of course, what they meant is that there are no mitzvos l'doros, for all generations - one of the requirements that the Rambam lists in his Sefer Hamitzvos (Shoresh 3). So all the commandments to count the nation, to set up degalim, to redeem the Levi'im, how to cover all the vessels when they move... None of those are part of the תרי"ג mitzvos.
So I am wondering:
a) Has anyone ever worked out a list of all these "temporary" mitzvos in the Torah? Don't eat the fruit of that tree; Avraham, lech lecha; Yitzchak, don't leave Eretz Yisroel; Yaakov, take your family and flocks and return; Moshe, don't go too close to the bush...; Eat the Korbon Pesach with your loins girded, staff in your hand... How many are there?
b) If no one has bothered, why not? Are they less important than the 613 mitzvos? - I spent a couple of years studying Zevachim, even though we can't do it (yet), and even though many great people who studied it died without ever seeing the Beis Hamikdash. Maybe I should also study how to stay away from Har Sinai, because we did it once? Is it so clear that there is a difference between our past and our future?
c) Nothing can be part of the Torah except what Moshe Rabbeinu taught us; afterwards, לא בשמים היא. What about one-time mitzvos? Is Hashem's commandment thru a navi (Go, speak to Achav. Your child will be a nazir from the womb.) any less a mitzvah than Hashem's one-time commands to Moshe, just because it cannot become part of the Chumash? Should those be counted too, if someone counts them?
Update: judging by some comments, I should explain (c): For sure any command by a navi is completely obligatory. I meant a different question: Is there a special category of temporary commands by a navi that are fundamentally different because they were actually given as mitzvos of the Torah. For instance, the laws of degalim were followed for forty years; the laws of wrapping the keilim when the mishkan moved were presumably followed for hundreds of years, up until the final move into the Beis Hamikdash. Same with all the laws of how to deal with heter bamos - all skipped by the Rambam. But when they learned Shulchan Aruch, that was part of what they learned, all that time. These seem to be part of Toras Moshe. That seems different to me from the one-time commands to Eliyahu - or for that matter even the one-time commands to Avraham Avinu which are quoted in the Torah but don't translate into a command to Israel. Or not.

Answer 1

I asked R' Tzvi Berkowitz shlit"a for his take. Here was his response [email]: "We study the mitzvos that we have even if we can't do them right now. The mitzva that Moshe Rabeinu was given to not come close to the bush was never given to us. The mitzva that the dor hamidbar had during the midbar was never given to us."

"never given to us". That's a really interesting way to describe it.