Generally speaking, porcelain crown restoration is not recommended before 18 years old, but there is not much difference between 17 years old.
As to whether it was misdiagnosed or not, no one saw the situation at that time, and no one could draw a conclusion, but it is debatable that the cheapest braces should be made in 900 yuan. If it is a private clinic, lz should consider it and go to several hospitals to see the price.
As for the material of 380, there is no way to know, only ask him himself.
In the case of lz, I give the following suggestions: it can be filled first, and it is not a big problem to make braces 1~2 years, but it depends on the filling materials and the technology of preparing holes.