NiOS II Processor

Hi,

I have some questions about the NIOS II Processor:
1) Which memory types can be connected with the NIOS core?
2) DSP and custom instructions – what is that?
3) Which memory types can be connected with the NIOS core?
4)Why the NIOSII is the “soft” processor?
5) What is differences between the SOF and POF files.
6)What is the designer platform tool for?