Is puberty different for each ethnicity? for example a stage in puberty may happen at a different time in caucasians than in hispanics?

There is a wide rage of variation to the timing of sexual development and you should read a little about it so that you can feelmore secure. https://www.researchgate.net/figure/Distribution-of-the-age-at-onset-of-puberty-in-the-cross-sectional-study-Histogram-and-a_fig2_23194869

Yes. Some data suggests different ages of onset of menses as a measure of puberty onset. May also be affected by diet.