They are all semi-finals. It takes 80 minutes to try 1, and it is much more difficult to try twice in half an hour (2 hours and 30 minutes) than 1. Finally, the total score is ranked as the first, second and third prizes.
The final is to choose the first prize in the semi-final to represent the province in the national winter camp (January), which is the final.
You have to take part in the preliminary contest of this province before you can qualify for the semi-finals.
I have participated in three semi-finals.
The preliminary registration generally depends on whether your school is organized or not. It's usually time for the preliminary round. If you want to participate, you should take the time to ask your teacher or the teacher in charge of competition activities in your school.
However, I would like to advise that the math contest is a long-term work, and we must go on happily on the basis of interest. If we are not sure, we must take our usual study into account when taking part in the competition. After all, the college entrance examination is the final choice for most people.