Can teeth that are naturally very yellow be whitened? If so, what is the best, long lasting way to whiten my teeth? (Photo)

Conventional whiten with a custom tray and Bleaching gel is the best way to whiten, and yes it does work on naturally yellow teeth,  though how well one whitens is unpredictable and cannot be guaranteed.I noticed on your photos some white spots.  Your whitening may not be uniform and may at first accentuate the white spots.  This will reblend a few days after you finish whitening, but you will always have the hypocalcified areas(white spots).  Covering them with a restorative material such as porcelain veneers would be a good option if you are not happy with the end result

There are many systems to bleach teeth, and you will never know how many shades whiter they can reach , until you do it, it seems that they are very yellow , i think you should try at least 2 systems, if the result is now what you expect, then veneers can give you what you are looking for, really white beautiful teeth.they can be done in just 2 visits to the office.