Are there only 6 episodes?

[Septimus Omega]

Are there only 6 episodes? The game I have started at the red wedding. Is there anything before that? Is there anything more after these 6 episodes? I have had this game for 8 hours and I am half way through?

When you finish it how different are the outcomes when you replay it?

Is it possible to discover content you didn’t see the first time?

[Ogami]

Yes there are only 6 episodes.
No there is nothing more after that. There was talk about a second season in 2015 but Telltale is busy with other games and they also want to wait for the tv series to end.
8 hours is actually pretty long for just 3 episodes. Most Telltale game episodes are around 90 minutes to 2 hours. Exeption the first season of the Walking Dead with around 3 hours per episode.
As for the outcome, the main story always ends the same way. You can influence who lives and dies of the Forrester family though.
And yes, there may be some scenes you did not see the first time when replaying and choosing other options, but only small ones.
In the end the story always comes back together on the main path.