Not currently on chain, but layer 2s and other external systems allow it. I believe Lightning already supports millisats (thousandths of a satoshi)

Yes, eventually. The prototol allows for more zeroes to the right of the decimal.

Imagine the scenario where that becomes necessary. "I'm sorry, 1 sat is worth way more than this loaf of bread--can I give you half a sat?"

#deflation

Not onchain.

I remember a bit on telegram using micro sats on lightning.

Not currently, but from what I understand if it becomes necessary it would only require a soft fork. I mean the price of Bitcoin would need to be $100,000,000 for 1 sat to equal $1 so we’re probably talking about another epoch or 2 down the road.