he is on visitor visa,if asylum is not approved, can he still stay in the US until his visitor visa 6 month period?
-Yes until the I-94 expires, but it is impossible for him to get the B2 extension due to immigration intent (asylum application is a very strong immigration intent). Also, it will affect him to get the visa to re-enter US in the future. So, unless he has very strong hard evidences for the asylum application, he had better not do that.