[Avodah] Korach Question

[Richard Wolberg]

If Korach questioned Moshe as to the authenticity of the Torah, at what point was the Torah already revealed?
In other words, the parasha Korach is part of the Torah.
Did Korach know that?  If so, he would know his fate.  If not, what part of the Torah was he claiming Moshe wrote on his own?
Also, wasn't Korach present at Har Sinai?  Didn't all the people hear/and or see the actual voice of HaShem for the first 2 Commandments?
So how could Korach, after witnessing this, deny it?