If a male develops a high voice and practices it daily and has a really nice singing voice that can go as high as to singing Usher, Rkelly + Songs, During and after puberty will that voice diminish and get lower as that there is no way for him to control or can he keep his voice to enter those high levels of notes..?

His voice will change like everyone, but as he practiced daily, he will be able to control it more than a regular person.
His ''pitch'' level might change, but he will still be able to get high notes.