There have been no reports of metal detectors affecting maps or programs in the speech processor. Many cochlear implant users attend concerts which use electrical devices and no problems have been experienced. That is an area of research right now. The current practice is to put it in the ear which has had better hearing over time. A promontary stimulation test can help decide which ear also.
Deep insertion is used now.
But the real goal is to get the electrodes as close to the nerve as possible. As the nerve comes to the cochlea, it divides. Small endings of nerve serve different parts of the cochlea. Implant insertion now covers many frequencies, both high and low. But there is a boundary between the ear canal and inner ear so it should be safe.