What's the game engine used by Bethesda before Creation Engine? And what's the last game make with it?
Gamebryo was the engine used by Bethesda before Creation Engine. It is developed by Gamebase Cot., Ltd and Gamebase USA. Gamebryo is used by numerous companies within the gaming industry.

Bethesda decided that Gamebryo's capabilities were becoming too outdated and began work on the Creation Engine for their next game, The Elder Scrolls V: Skyrim, by forking the codebase used for Fallout 3.

The last game from Bethesda made with Gamebryo engine is Fallout 3 (2008).