Yes modern AIs have an entire opening database and generally have cached the first 20+ moves of the game (for most common openings) from a database of very deep searches identifying the best move. This is absolutely a form of opening prep for AIs.
That said, even without that database a modern AI will completely topple the best human at every common chess variant. Humans cannot defeat modern AIs in chess like games.
That said, even without that database a modern AI will completely topple the best human at every common chess variant. Humans cannot defeat modern AIs in chess like games.