Second, you can apply for military schools during military service, but does it mean that you have retired? Then you want to go to military school? This is not easy. It needs to be retested according to local personnel. If you are in service, generally speaking, you will enter the military school in the second or third year.
Third, I don't quite understand what you mean by "staying in the team" as a soldier. But I can tell you that when a soldier is promoted to a cadre, he can definitely stay in the barracks, become a non-commissioned officer or become a volunteer. It's hard to say whether it's easy or not. Depends on personal performance.