1. You do NOT grow more white hair by plucking them. 
2. An undercut does not always mean a shaved side/back.
3. Getting regular trims will not make your hair grow faster; they just prevent split ends from moving up the hair shaft.
4. You can still apply oil products regardless of an oily scalp. Just apply on mids to ends.
5. Stress does not cause gray hair. It all depends on genetics and age.