But where is it stored? It is done on the old client, if it is not visible in the network, how does it display on the new client?
When you update to new client, you still have to use the previous wallet.dat file to restore your wallet which dtull have the same data of previous wallet.
It has no option to cancel the transaction if the transaction is made within 14 days, right?
I don't know if it's 14 days. If I can remember correctly, I was able to remove after 7/8 days or so. Usually, when it's get dropped from mempool (I have a little discussion now though.).