JavaCard OS

I am getting started with java card OS development. Now i have some primary questions about this.
Could anyone give me any direction ? Thanks a bunch.

My questions:
1. Can I develop the java card OS in C/C++?
2. The compilation of the java card OS code must be based on target IC, am i right?
3. How could I load the the compiled code into the memory of the 'blank card' ? Should I use any tools or execute commands?
4. Please tell me anything about the memory location when loading the OS into the java card.
5. If the card is GP compliant, should I add the GP support part?

Q1: You can use C/C++ to develop the java card OS.
Q2: You are right. The card manufacturer shall provide a tool chain for this.
Q3&4: It depend on the card you use and you should refer to the developer documentation that the manufacturer provide for you.
Q5: If the card is GP compliant, it will most likely have a JCRE as well. If you are building a JCRE, you need to add the GP support part.