i don't know if its possible or not that why i'm asking about cancel bitcoin transaction using double spending
imagine that you put wrong address's receiver and wanna cancel transaction if what i said is possible so you can send same amunt to another addres (one of yours) and like that you have 1/2 chance to cancel your transaction.
Finnaly if that all is true and possible can we consider it legal or no. ?
Additional to what Danny said Id like the emphasise that the two transactions do not have an equal chance to get confirmed. The chance greatly depends on the details of each transaction, but lets consider a "normal" transaction with appropriate fee and all inputs are confirmed. You send your first TX (A), modify your client to forget about it and send your second TX (B). Now most of the nodes in the network will know about A within a couple of seconds. By the time you have modified your client to create B almost no other node would accept B, because they already know about A. Thus your chances to get B confirmed instead of A are infinitesimal.