Can a bitcoin exchange or any altcoin transaction be cancelled due to error?

[Icologies]

can a BTC exchange be terminated before it has been affirmed, or is it that once communicated it is beyond the realm of imagination to expect to drop whenever

what is the meaning of you when the transaction or exchange occurs an error and hopes to return? I don't think that can be done, errors that are not from the system cannot be undone. Then from that when transacting, prioritize accuracy and read again if necessary and make sure the exchanges done are not error.

[omone1]

The blockchain is an immutable technological structure. Once anything has been transmitted through it, it can never be reversed or altered. One a bitcoin transaction has been sent and confirmed, it can neither be cancelled or reversed. That is a tampered proof.

[wywoc]

can a BTC exchange be terminated before it has been affirmed, or is it that once communicated it is beyond the realm of imagination to expect to drop whenever

If your transaction was sent to blockchain, it can not cancel. So be careful if you want to make a transaction. Or sometime your order has not been executed, exchange's support can cancel the order before it is on the blockchain. In my opinion that is the only way now.