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.

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nilslindemann an hour ago | parent [-]

Like my answer below, that's wrong. Even I have achieved a few draws or even wins against Stockfish in training games, and I am FM strength. From time to time you are happy to reach a simple rook endgame which happens to be won and the engine doesn't anticipate that (horizon effect). You still draw or lose 90% of those but you win 10%.

	▲	galkk 34 minutes ago \| parent \| next [-]
		Either the engine was misconfigured, the hardware you were playing on was glitching or you are omitting something. There is no chance in the world that you can beat stockfish in standard time control.
	▲	nilslindemann an hour ago \| parent \| prev \| next [-]
		Further, if the engine does not use an opening database and the thinking time per game is the same, then the engine will usually make the same moves, so you can learn from your errors. There are just a few chess engines which "learn" per default and therefore change their moves, like BrainLearn.
	▲	LogicalRisk 23 minutes ago \| parent \| prev [-]
		That's an extraordinary claim. What level was Stockfish and what were the settings for these training games?