in reality of bitcoin transactions that we canno't cancel transaction made even its not yet confirmed
It depends on the exact circumstances of transaction. In most normal situations, it is very difficult and unlikely that you will be able to stop a transaction once you send it.
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.
In most cases that is not possible. Most peer nodes will reject and ignore the second transaction since they will already have seen the first transaction. There are a few special circumstances where miners may not have seen the first transaction yet, and other special circumstances where miners may have forgotten about the first transaction after some time has elapsed.
Finnaly if that all is true and possible can we consider it legal or no. ?
That depends. If you are doing it for the purpose of fraud (to gain something of value from someone while failing to deliver bitcoins that you agreed to deliver), then in most jurisdictions it would be illegal.
If you are not attempting fraud, then in most jurisdictions it would most likely be legal.