W3D1 tutorials questions

Dear all, I need your help in clarifying explanation in tutorials of real neurons:

1- Tutorial 2, I couldn’t understand the relation between mean, standard deviation, input c, exc. rate, inh. rate with CORRELATION
I can see if we changed any of this parameters, correlation changes, but can’t describe the changing behavior, it seems for me random.
Is there a systematic relation between these parameters and output correlation?

2- Tutorial 3, What is the reversal potential and why current is equal to zero although it is above threshold? I don’t understand this sentence in the tutorial video. Anyone does?

3- Tutorial 3, what is meant by ensemble rate?

4- What is the free membrane potential? it was defined in the tutorial as when the threshold is very high that the input signal can’t reach, but later there was a case of mean of FMP above threshold discussed? What am I missing?

5- Dear all, In W3D1, Tutorial 3, I am not well understanding the drawn relation between conductance and (u and R), if anyone has another explaining material, please provide it.