Not a market order which majority of people on Robinhood are using market orders since they are the default. Most don't even know what a limit order is I'm guessing.
The answer to your break point question is yes. You can debug your C# code on the front end with breakpoints. The biggest benefit is applications with a lot of domain business logic tend to have that logic copied to the front end and copied to the backend. If a object can no longer be updated if it has an expired date then you would have logic on your server to prevent that. You would also have logic on your front end to display to the user that this can not happen before even going to the server. The server would act as a backup and ensure it never happens.
With Blazor, this logic only exists in one place which helps follow DRY.Logic that is duplicated tends to get missed in testing often. This provides business value.