Which was the wall Titan Eren sealed with a rock?
Wall Rose was sealed in the anime. That wiki may contain spoilers from the manga, so read carefully.

From wikipedia: (https://en.wikipedia.org/wiki/List_of_Attack_on_Titan_episodes)

Episode 10: "Pyxis asks Eren if he will transform himself to block the gap in Wall Rose to prevent more Titans from getting in."
Episode 13: "With the gate finally sealed, the army eliminates all of the Titans remaining in the Trost District except two".
The Trost district, being, of course, on the edge of Wall Rose.