My take, for what it is worth!

Extracts:
Originally Posted by Lana
My take, we do know Fredo undoubtedly knew "about the Senate hearing" which Fredo "deliberately and deceitfully concealed even after his betrayal, the Tahoe shooting then cunningly withheld" the information from Michael
Originally Posted by Capri
Fredo undoubtedly knew "about the Senate hearing" which Fredo "deliberately and deceitfully concealed even after his betrayal, the Tahoe shooting then cunningly withheld" the information from Michael -- Michael prison Fredo Don
Originally Posted by mustachepete
I'm not sure how the word "undoubtedly" is supposed to function there. For all we know, Fredo had some glancing contact with Questadt in Havana, and was as surprised as anyone to see Questadt on TV with the senators

Boathouse dialogue
Quote
Extract: What about now Is there anything you can help me out with Anything you can tell me now

My take, Fredo seemed to know now meant the Senate hearing and also knew -
  • They've got Pentangeli
    [committee will produce a [star!] witness who collaborates the charges that were made against Michael and at which time Mr. Corleone may very well be subject to indictment for perjury]
  • Questadt belongs to Roth

Hence my conclusion that Fredo -
1. had prior knowledge of the Senate hearing
2. withheld information that may very well be detrimental to Michael

Roth or Barzini? Whose plan was the best?
Originally Posted by Evita
Extract: Knowing or not knowing about Questadt made no difference whatsoever to Mike's defense Good or Bad

He had already taken the necessary measures by bringing Frankie's brother over

Whilst Fredo's concealment of the Senate hearing and withholding of the information Fredo knew, from Michael, ultimately made no difference whatsoever, the fact remains, Fredo never volunteered what Fredo knew even after the first hearing Why?