What happens if a character's stats are lowered, reducing the number of spells they can prepare? [duplicate]

Question

What happens if a character's stats are lowered, reducing the number of spells they can prepare?

Say a level 1 cleric has a Wisdom score of 18. According to the Spellcasting feature , they can prepare 5 spells (Wisdom modifier of 4 + 1 level of cleric). Now say the cleric obtains an ioun stone of insight and attunes it. They now have a Wisdom modifier of 5, so they can prepare 6 spells and do so.

What happens if they then unattune to the ioun stone?

The rules say they can only prepare 5 spells again, but they don't indicate that the character automatically loses one prepared spell from what I can see.

Answer 1

The Cleric's Spellcasting feature states about preparing spells:

You prepare the list of cleric spells that are available for you to cast, choosing from the cleric spell list. When you do so, choose a number of cleric spells equal to your Wisdom modifier + your cleric level (minimum of one spell).

When preparing a spell list, you create a whole new list; you do not add or remove spells.

If you are a level 1 Cleric with 18 Wisdom, then you can prepare 5 (4 + 1) spells.

If you have the Ioun Stone, then you can prepare 6 (5 + 1) spells.

If you unattune the Ioun Stone, then you can prepare 5 (4 + 1) spells.

If you were to attune the Ioun Stone and then prepare 6 spells, then unattune the Ioun Stone, you continue having the 6 already-prepared spells. When you decide to prepare a new spell list, you will only be able to prepare 5 spells.