Hello Takepiro,
1. There are no internal pull-ups on the MPx pins when configured as inputs.
2. These registers can be configured in SigmaStudio under the Hardware Configuration Registers window under the "DSP Register Modes 1" register option.
3. When you refer to SPORT, do you mean the SPI or I2S serial port? As long as there is no crosstalk that can affect the integrity of the clock signals, there should be no negative affect of SPI or I2C accesses as this operation is asynchronous to the DSP serial port operation.
However, if you meant the SPI CCLK clock running at 22 MHz, note that the ADAU144x datasheet states that the SPI port's CCLK can write data to the ADAU144x at 32 MHz, but reads are limited to 16 MHz CCLK max frequency.
-JT