I think option 2 is the correct one. Keep in mind that Fredo knew Pentangeli was alive and that Questadt belonged to Roth. He had to have obtained this information well after the attempt on Michael's life, which means he kept in touch with Roth and Ola. He probably did tell them how Geary had been compromised, and I am sure Roth would have seen to it that Geary be in on the plan to set Michael up for perjury. A word from Questadt .."Senator, my friend in Miami can take care of any of your troubles with Michael Corleone. We'll establish that Cicci killed people when he got orders to do it, and then you do what you can to give rise to the impliction that Mr. Corleone
was the head of the family. Once you've done that you can leave the committee to handle that other matter."

On a related subject, the ongoing relationship between Fredo and Roth would have been further reason for Michael to have him killed.

Also I wonder if Roth and his people had a hand in getting Fredo out of Cuba. Fredo was certainly no genius, but somehow he apparently made it to New York. When he got there maybe the Rosatos took care of him.