Oral Torah

Paid!!
Does the rabbi have a column that talks about defining the Oral Torah?
I heard in Rabbi Moshe Rabbeinu’s class that he didn’t even know what the 19 Avot Melacha was. I would love to understand what the Rabbi meant. Did Moshe Rabbeinu inquire and write on Shabbat but not chop wood?
How much of what is in the Gemara is from the Amoraim and how much was actually given at Sinai? It is possible that even totefot were not the tefillin we are familiar with at the time of Moses or the First Temple, for example? Why was the written Torah given without interpretation and how did it get along for thousands of years without an agreed interpretation and everyone had their own personal interpretation and suddenly the Gemara wrote all the explanations
 
After all, our argument against the Karaites is always that how can one keep the Torah without an accompanying commentary to the book, and now I discover that for us too, these things were not truly received along with the Torah and created over the course of generations?
What did they observe when Moses our Lord descended from Sinai?