C'est malheureusement le second choix. Le "can't" prévaut sur le reste. Le cas est même précisé dans la F.A.Q. de la carte, en fait.
"When you reveal this plot as a result of triggerring the Rains of Castamere, the claim for that INT challenge would be 2 and you will not be able to initiate any more challenges that round.
The word "cannot" supersedes other rules which could allow you to have more challenges. It makes almost no sense to play this within the Rains agenda unless you want to have some surprise "Trial by combat" 2 (or 3 with core Cersei) MIL claim"