I just bought NFC reader from: NFC Shield V1.0 | Seeed Studio Wiki
It is stated that: SPI interface. Hence, most Arduino pins are available for other applications
So can I still be used pin 9,10,11,12 for other bit transfer because it has already use SPI?
Or I cant?
Pins 11, 12, and 13 are the SPI bus pins. You can connect more than one SPI device to those pins, as long as each has a different SS (slave select) pin. Pin 10 needs to be set as an OUTPUT pin (and otherwise not used, except possibly as a SS pin) to define that the Arduino is the SPI master.
You can use these pins to talk to any number of SPI devices, but not for other purposes while there is a SPI device in use.