Ryuji-san,
Please see the responses for each set of pins below:
(1) GPIO1~3
By default, these pins are configured as inputs. If their state is not explicitly changed, a weak 1M pull down could be used on these inputs to park them to a known state. However, if the function or direction is changed (GPIO 3 supports an active low PD on the TSSOP package, for instance) care needs to be taken to ensure that the external pull resistor does not conflict with the device functionality.
(2) SDO, SDI , SCLK, CS
You are right. No pull-up or pull-down is required.
(3)NC pins
NC pins may be shorted to GND.
Regards,
Sandeep