JavaCard OS

I have a question. Maybe this question is stupid. ISO/IEC 7816 is mentioning that SW1 value should be in the interval 61-6F, must I use the value within the area of 61-6F ? Or is it up to me, which SW1 values I will use for responses. For the success response I think that SW1SW2 value should be always 0x9000, right?

0x9000 is used for success. If you can find an ISO7816 SW that matches the error condition that you are trying to indicate, I think it is a good idea to use that.