Please help me in understanding these

1.  If the Questions ask about THREE POINT ESTIMATE , which formule should I choose, as in one of the mock test, I used (O + 4M + P)/6 , but the answer was (P + M + O)/3, though it was not mentioned that its a triangular distribution

2. How to differentiate between Risk Exploit and Risk Enhancement , any examle would be great 

3.  Risk Mitigation & Risk Acceptence  -- I understand we need to have contigency reserve  to accept risk , but in some mock test, some action has been taken for the accepted  risk. This confuses me as to how to differntiate between Risk Mitigation and Risk Accepetence.

4. If senior Mgmt ask,  whether  the project will meet the expected budget, which EVM  value will you share.

Answer was TCPI  and I thought it was CPI.