Sounds like you haven't wrapped your head around the basics of smart contracts.
Yes, a blockchain gives you an (ideally) immutable foundation. No, that doesn't mean that every transaction that invokes a smart contract has to be immutable. If a smart contract for a particular use case needs to have the ability to "backtrack", so it can, there's nothing stopping it.
Yes, a blockchain gives you an (ideally) immutable foundation. No, that doesn't mean that every transaction that invokes a smart contract has to be immutable. If a smart contract for a particular use case needs to have the ability to "backtrack", so it can, there's nothing stopping it.