Depends on the test. A hair sample would show positive.
no it would not still be in your system if you took it over a month ago. pain pills only stay active in your system for up to two weeks. now lets say you took it a week ago all you would need to do is detox and it would be out of your system before the two weeks.
You will likely test positive.
It's okay if you had a rx for it.
I don't know how long it takes to clear it out of your system, but it should be google-able.