Have you considered going to dental school yourself ?

Then you could answer your own inane questions.

The bottom line about OTC whitening products is they are not as
high a % concentration as what is available from the dentist.
This is by law and not by our choice, the higher strength bleaching
agents are only available by Rx or to practioners.
Contact the DEA and FDA if you dislike this arrangement.

"Power" whitening such as Zoom! is done with a special
activation light which is not available to patients.
It works, and quite well.

Not all teeth can be bleached with the aforementioned technics.