Geoffrey was a monster to begin with; admittedly, at the very beginning he is more reliant on his mother than at the end (when he defies her), but he was a monster either way.
Backstory isn't development. It's explanation, not change. Their characters remained the same (to both their downfalls). It's good that it was there as it deepened the character and made them more empathetic but it didn't develop them.
Tyrion, uh, I kinda agree. Personally I feel that his defiance of the Queen and *****slapping Geoffrey showed he had a powerful personality, while his lustfulness was in full display from the very first episode onward. I don't feel that's changed too much. Again, more backstory, no development. However, I guess you could have missed the strength of his character and have had that pointed out throughout the series. It's kinda obscured in the first couple of episodes.
Snow did see some development. Disillusion, mostly. But in the end, he didn't really change. He chose to stay with the Night's Watch for the same reason he joined them in the first place: that doubt entered him was development, but ultimately it didn't lead to a permanent change of character, so tbh I don't consider it noteworthy.