Friderick II of Prussia is accidentally killed in August 1759 during the battle. Prussia is completely demoralised and begs for peace, and eventually ends up being reduced to Brandenburg and Pomerania, with Russia taking East Prussia and Austria taking back Silesia. I seriously doubt it would meaningfully influence the other part of Seven Years' War, so France is defeated just like OTL. The results I see:
1. No Partitions of Poland until the French Revolution, since Friderick is killed and Austria and Russia are unwilling.
2. Austria wins the War of Bavarian Succession and annexes Bavaria
3. Austria is more successful in fighting the Ottomans, so Bosnia is taken from them (or at least a part of it) roughly a century earlier.
Upon the death of Elizabeth of Russia Peter becomes the new Emperor, but only to be deposed as IOTL. True, he can't hand over East Prussia back to Friderick, but there were plenty of other reasons. But perhaps he himself or Catherine later on could hand over East Prussia to Poland in order to make the Poles more loyal? Or that's unlikely?
And when the Revolutionary wars start, how would the absence of a strong Prussia affect them? I see Friderick William becoming a French ally quite early.
1. No Partitions of Poland until the French Revolution, since Friderick is killed and Austria and Russia are unwilling.
2. Austria wins the War of Bavarian Succession and annexes Bavaria
3. Austria is more successful in fighting the Ottomans, so Bosnia is taken from them (or at least a part of it) roughly a century earlier.
Upon the death of Elizabeth of Russia Peter becomes the new Emperor, but only to be deposed as IOTL. True, he can't hand over East Prussia back to Friderick, but there were plenty of other reasons. But perhaps he himself or Catherine later on could hand over East Prussia to Poland in order to make the Poles more loyal? Or that's unlikely?
And when the Revolutionary wars start, how would the absence of a strong Prussia affect them? I see Friderick William becoming a French ally quite early.