I am using AD5421 in my design, I have below queries on SPI
I will provide IODVDD to AD5421, but loop power is not given
What will be the state of MISO lines, whether SPI sections of IC works?
The logic controlling the SDO pin requires DVDD which is coming from the loop power.
Given your case, the it is likely that the SDO will not behave as expected. The part should also not be able to respond to SPI commands.