Is it possible to be 19 in the 10 grade of high school?

Yes it is, this happens more often than you think. you can be pulled down a grade if your marks do not reach the required mark to pass on to the next grade. This only means you stay in the grade you are and redo another year. It isn't all bad, this is also another opportunity to learn more and be more ready to pass grade 12.

I think schools have a limit to what age you can be to stay in a school but you can definitely stay even if you are an adult.

While possible, you really shouldn't be in your second year of high school at the age where most people are in their 1st or second year of college.