My take, for what it is worth!

Among others,

Did Roth engineer the cop’s entry into the bar, thwarting Frankie Pentangeli’s assassination? (This thread gets the Lifetime Achievement Award.
I believe the killing of Frankie was abandoned because of the unexpected entry of the cop

Then the ever astute Roth used Frankie's 'attempted' [Michael Corleone says Hello!] killing by Michael to his advantage as his Plan C the Senate inquiry ["The Senate lawyer Questadt belongs to Roth"] after Plan A Tahoe bedroom shooting and Plan B Michael's 'accidental' death in Cuba

Frankie should have had more faith in his Don irrespective of how it is deemed he got “kicked around” However Michael did hang Frankie out to dry What happened to the Capo's family being taken care of after the capo's death?

Who killed the Tahoe shooters?
I believe there was a third [!] assassin who took care of the first two assassins who were probably told to wait by Fredo's bedroom for assistance but were always going to be killed to leave no loose ends

There was a car at the gates trying to drive off or something just after the gun fire and Michael's guards were shouting Stop! Stop! then Halt! Also the sentry was slack leaving the gates open

Was Michael wrong to kill Fredo?
I believe so Michael having his brother Fredo killed was unforgivable and unnecessary, especially considering Michael was able to keep Fredo under watch or similar until Mama Corleone's natural death “It really did break Michael's heart”

Would Sonny have made a better Don than Michael?
As Vito himself said Sonny was a bad don As Virgil Sollozzo said Sonny was a hothead and can't talk business with him

If Clemenza (rather than Pentangeli) had been in GFII, would he have betrayed Michael?
I don't think so Besides it would have been so uncharacteristic considering the Clemenza we knew in The Godfather He was like a second father

Why didn’t Robert Duvall appear in GFIII?
Robert Duvall felt the pay gap between Al Pacino and him was unacceptable
https://www.youtube.com/watch?v=4kFpSMLPl58

Who was a better Don: Vito or Michael?
In my opinion apples and oranges

The Mafia business is kill or be killed The bonus for Vito was his wife Carmela

I believe both Vito and Michael were the best Dons they could be, under their respective circumstances Times were changing

The most significant difference is Vito's wife Carmela never questioned Vito about the business. Carmela's love, loyalty and support for Vito was unconditional
So Vito never had to worry about the blood family at all When they married Vito was a law abiding shop employee in a grocery store and only became Mafia after

Vito never had wife nor siblings problems including betrayal Vito never even envisaged the fury, resentment, hatred etc, that Fredo and Connie would harbour towards Michael and actually acted on

In fact Vito planned all the dirty work – killing of Carlo Rizzi and Moe Greene, the baptism murders – for Michael to carry out after Vito's death thus leaving a murderous legacy for Michael

If it is deemed that Michael didn't separate himself from his emotions like Vito knew “how to and did” in my view Vito did not either [Don Ciccio's murder] however because of Vito's family set up there were no consequences

Vito went back years later and killed, a senile, one leg in the grave, Don Ciccio who was living out his last days thousands of miles away absolutely no threat to the Corleones as revenge for killing his family because same as Michael the enemies have to be wiped out

If Michael's wife Kay was like Carmela, Michael would have had it all! When they married Kay knew Michael was Mafia

Who opened the drapes in Michael's bedroom?
Arguably, Fredo opened the window drapes thus 'identifying' Michael's bedroom