May I please add a couple of questions
Sorry, if already discussed, I'd appreciate the link Thanks

Whilst having drinks in Havana, so that the brothers can spend some time together, especially when Michael didn't want Fredo to do anything, just go along with it

Why did Michael tell Fredo “Hyman Roth will never see the New Year"

Among others, Fredo had just told Michael that
1. Perhaps a bit of envy - not having married a woman like Michael's wife, Kay [oh, boy!] having kids etc.
2. He was mad at Michael [why?]
3. Why didn't [Fredo and Michael] spend time like this before [before what?]

As far as I can recall, except for the Sollozzo drugs meeting, Fredo had not been privy to the family business thus far

Fredo didn't even know that the Corleones were wanting to buy out Moe Greene's share of the hotel or that Vito was semi retired or what the $2M dollars was for

Was Michael trying to console Fredo that Fredo was no gypsy!

At that time Michael still had not found the traitor in his family

Michael seems to be giving pondering looks at Fredo but if he had the slightest suspicion Fredo was involved, he would never have revealed such an important hit, in Roth friendly country too – it could have jeopardised the whole operation. So risky
[well, Roth did survive but reckon not because of Fredo Then again Fredo did try to 'disappear' on the pretext of getting a real drink!!]

There was too much at stake for Michael to use the Roth hit as bait, to test Fredo

So uncharacteristic indeed and hard to fathom, why Michael was suddenly inclusive of Fredo

Why did Kay leave the children in the unholy and evil environment?

Kay's abortion makes no sense as no doctor would dare abort a Corleone child!

I believe Kay might have miscarried perhaps the trauma of the bedroom shooting

Michael had already said
“Kay, what do you want from me? Do you expect me to let you go? Do you expect me to let you take my children from me? Don't you know me? Don't you know that that's an impossibility that could never happen. That I would use all my power to keep something like that from happening Don't you know that”?

Then when Kay realised it was an 'impossibility' used the abortion, for Michael to allow her to leave him, during her "unholy and evil" speech at Hotel Washington

How can Kay as a mother leave their children [according to Kay] especially Anthony who is 'not' fine, in the unholy and evil Sicilian thing, with the father who is 'blind' to everything other than business and the children's friends are Michael's buttonmen?

I believe as a mother Kay should have at least taken up the second chance Michael offered and tried to salvage the situation for the sake of their children

Michael seemed stunned by Kay's outburst and would have been forced to make the changes he promised in the beginning of the conversation

Also, Kay says she knew “no way Michael could ever forgive her” makes me to wonder even more that it was a miscarriage because what mother would 'abort' their child to spite their father Now that is unholy and evil!

And Michael was sprung by Kay in front of Rocco! Fancy telling Michael that “children are outside, we are going” in front of a buttonman!

Also Kay didn't seem happy! that Michael was “too smart to let any of them beat him”

It seems Kay did not know Michael after all